All right, after reading the 1000 th “I just found this site, and my friend has a Vulcan AR 15 for sale, is it a good deal” thread, I though about putting this together for the newbie.  This is a compilation of a lot of the stuff I have learned from spending way too much time around here.  Its also a lot of stuff I wish I had known before I started putting money into rifles.  I am far from an expert, so if you see errors (in facts not opinions) please let me know.  I also could use help with details on the different brands and what they offer.  Please share your knowledge.  I am still working on this and will edit as I have time:

So you want to buy an AR15:

First you should decide on what format you want, lets take it one piece at a time:

BARREL[/b]:
This is probably the most important decision you have to make, as it is the heart of the rifle.  

Length:
The original M16 had a 20” long barrel.  As the platform has evolved, all kinds of lengths have developed.  The 20” barrel has some advantages- including greater velocity and longer sight radius than shorter barrels.  The increased velocity is important if you are going to be shooting long range (say over 300-600 yards) or if you are going to be shooting at something which can shoot back at you.  The latter is true because some military ammunition relies on fragmentation, (the bullet yawing and then breaking up inside the body) in order to cause damage and stop a person/animal.  The faster the bullet is traveling, the farther out it will have enough velocity for the bullet to fragment.  Look at the  "Ammo Oracle" to learn more about this, as well as more than you could possibly ever remember about AR ammunition.  The increased velocity has another advantage, in that the bullet will have a flatter trajectory, and thus hitting objects at unknown distance will be slightly easier, as errors in estimating the distance, or correcting for bullet drop or wind drift become slightly less important.  The increased sight radius is useful, as it improves the shooter’s ability to shoot accurately.  Because the front and rear sights are farther apart, any error in misalignment at the time of firing will be smaller as it is extrapolated out to the target.  Note that the longer barrel is not more accurate, the sight radius simply makes it easier for the shooter to shoot accurately.  This advantage disappears as soon as a telescopic or red dot sight is added to the equation.  If you want to shoot at very long distances, for example long range target shooting, varmint hunting or sniping you might consider a 24” barrel.  This increases your velocity, and adds to all of the advantages noted above except sight radius.  Most 24” barrels use the same sight radius as the 20” rifle, unless they are specifically set up as a “race gun” for long range target shooting.  

The next common shorter length is the 18”.  I believe this length either evolved, or was made popular due to the SPR “Special Purpose Rifle” concept.  The idea here is to have a rifle used by someone who is a better than average shot in a sniper type role, without going to a full blown sniper rifle.  The goal is accuracy at long range, and the 18” is seen as a good compromise between the 14.5” M4 and the full 20” rifle.

The next common length is 16” which has evolved because of our laws in the US.  The Army (feel free to correct me if I am wrong, I am not in the military, nor do I claim to be an expert on this) has decided that for the most part a shorter barrel is more useful.  They have gone to the M4 which has a 14.5” long barrel.  In the US it is illegal to own a rifle with a barrel shorter than 16” unless it is registered as a “short barreled rifle” which requires special paperwork and some extra $ to the .gov folks.  Thus evolved the 16” barrel.  The advantage to this is that you have a barrel which is handier to move around with, swings easier, is lighter, and you don’t have to register it and pay extra dough to the government.  Probably the 16” is the most common length these days, most shooters having agreed with the army’s assessment that you don’t gain that much with the extra 4”, and the compromises are worth it to have a quicker handling gun.  This is especially true for civilians who are not limited to FMJ ammo, and can select an ammunition which is not as dependent on fragmentation and velocity for self defense.  It should be noted that the original 16” barrels used the “carbine length” gas system.  This means that the distance from the chamber to the gas block (front sight base in most cases) on the 16” barrel is the same as what the military uses on a 14.5”.  This distance is significantly shorter than the distance on a 20” barrel, because the gas pressure forcing the carrier and bolt backward only exists while the bullet is in the barrel.  This pressure has to be present for a critical length of time, and thus with a shorter barrel, that time has to start sooner in the cycle.  This results in a harsher recoil than one sees with a rifle length gas system, and potentially more problems with extracting the bullet from the chamber, as the rifle is now trying to do this while the pressure in the chamber is higher.  The smart folks at Armalite came up with the idea of moving the gas system in the 16” rifle down the barrel a ways from where it would be on the 14.5” design, and they invented the “midlength gas system” (middy for short).  This design is slightly easier on the components involved, as there is slightly less pressure in the chamber when the rifle is trying to extract the bullet, and there is less force transmitted to the carrier.  This design also gives a slightly longer sight radius, and also allows the attachment of a normal designed ever important bayonet.  

Obviously, the 14.5” is next.  There is actually a way around the law noted above concerning SBRs that we should note here.  If you attach an “extended” flash hider (Smith Vortex, SDI Extended A2, YHM Phantom, VLTOR Compensator, etc.) flash hider to the barrel in a “permanent” manner (for example by threading it on and then drilling a hole off center and driving a pin through it to keep someone from removing it) and the overall length of the combination is 16” or more, you have met the requirements.  These barrels are usually referred to as 14.5” with pinned flash hiders.  The down side to this is it makes things a little more difficult to remove the barrel and install most free float tubes, as with most the flash hider (FH) and front sight base (FSB) have to come off to install them.  There are two piece free float rails which can be used to get around this as well.  Again, the gains are maneuverability and portability, with the trade off of shorter sight radius and less muzzle velocity.

Once you get shorter than 14.5, you can go as far as you want.  These rifles are designed mostly for shooting things in cramped quarters, and for easy maneuverability.  The trade off is again lower velocity, and now significantly increased muzzle blast.  These guns tend to be more particular about type of ammunition used, gas port location and size and need to be set up exactly right to run well.  This is a fairly specialized area of ARs in my mind, and I have limited knowledge in this area so maybe someone else will come along to supplement my knowledge.

Material:

There are three common materials used in making barrels: 4140, 4150, and stainless steel (I believe 416 is the most common).  Each has advantages and disadvantages.  4150 is the spec (as I understand it) for the military.  There have also been discussions of 4150vs CMV which are over my head.  Some companies use these terms interchangeably, and others do not, some will list their barrels as “4150 CMV“ while others will use one term or the other. In my mind these terms are interchangeable, but if someone wants to straighten me out, have at it  Regardless, 4150 is apparently somewhat better than 4140 in standing up to the heat and abuse from full auto firing.  I am not a metallurgist, but the folks who seem to know on page two say that the "40" vs. "50" has to do with an amount of carbon in the steel.  More carbon gives a stronger steel, which is slightly harder to machine, but also more durable.  The consensus seems to be that 4150 slightly better, slightly more expensive, and possibly a little harder to work with, but the differences may not be detectable in a rifle which is not used to shoot full auto.  

Either of these materials can be chrome lined.  Chrome lining is a process which bonds chrome to the inside of the chamber and or barrel in a very thin layer.  This is advantageous in that the chrome lining is harder and has more “lubricity” or “slipperiness” than the underlying chrome moly steel (4140 or 4150).  This extends the life of the barrel (possibly 2-3 times as long) as well as making it easier to clean.  Some companies offer only chrome lined barrels, some offer both, and some offer only non chrome lined.  The general consensus seems to be that chrome lining is easily worth the few extra dollars you pay for it.  It does have one down side, however.  The process of bonding the chrome to the inside of the barrel is not as exact as the process of cutting the barrel in the first place, thus overall chrome lined barrels are SLIGHTLY less accurate than non chrome lined barrels.  This is a generalization (as evidenced by the impressive accuracy of the FN SPR series which usually shows incredible accuracy in spite of having a chrome lined barrel).  Most shooters will never notice the decrease in accuracy seen due to chrome lining, but if you are that good, and it is that important to you, then think about getting a rifle without it.  Many say that the amount of accuracy lost is less than or equal to ½” at 100 yards, so if you shoot Wolf like me, you will never see it.

The final common material is stainless steel.  Again, this seems to be a material which become more popular due to competition as well as the REECE/ SPR/ DMR evolution.  Most stainless barrels are designed for accuracy.  Obviously the alloy of stainless is designed to be less susceptible to corrosion, something which the chrome lining of a chrome moly barrel offers, but without the downside of decreased accuracy.  Stainless is not as corrosion resistant, nor as durable as chrome lining, but is used where one decides the trade off for better accuracy is worth it.  As I pointed out above, most shooters will not benefit significantly form using stainless, as either they or their ammunition is not accurate to see the difference.  There have been some recent threads about the durability of stainless which have been fairly impressive, and obviously it has been meeting the needs of the military for a while now, so if accuracy is your main concern, consider stainless.  Stainless is not usually chrome lined, but there have been a few custom runs of chrome lined stainless.

How long do these materials last?  Good question.  I have seen numbers tossed around concerning a chrome lined barrel lasting around 20,000 rounds (lets see: $200 for 1000 rounds of wolf... ?$4000 worth of cheap ammo?).  There was a thread by one of the industry sponsors outlining a SBR with a stainless Wilson barrel with 16,000 rounds through it which still had decent accuracy.  A non chrome lined non stainless barrel is often said to last half as long as a chrome lined one.  Remember, that the military definition of "accurate enough" is no where near the same as someone who shoots high power rifle, and regularly goes out to 600 or more yards. Also, you bumpfiring fools, or full auto guys will get less life out of a barrel because as the barrel heats up, it becomes more susceptible to wear by continued firing.  Thus, YYMV (Your Yardage May Vary).

Profile

The profile of the barrel is the shape it was turned to on a lathe.  This can range from a barrel designed specifically for accuracy which is 1” diameter, down to a “pencil barrel” which is designed to be light weight and handy to maneuver with.  A great resource for learning about profiles can be found on Randall’s “AR15barrels.com” website here: Barrel Profiles.  He shows all the common profiles, and I believe even has a chart showing differences in weights here:  Barrel weight PDF link.

Of minor note.  The finish used on most non stainless barrels is called “Parkerizing”.  Some companies parkerize the barrel before placing the front sight base on, and some after, which results in much wringing of hands and slinging of mud when their respective fans (known affectionately as “kool aid drinkers) defend their favorite brand.

The barrel can be lightened further by adding "flutes" which are usually grooves added to a barrel to lighten it.  This not only removes material to make the barrel lighter, but also increases surface area to assist in cooling the barrel.  Occasionally you will see someone say that fluting a barrel will make it stronger.  This is not true, as I understand it.  The strength of a barrel is determined by its cross sectional area, and any time you remove material this will decrease.  What you gain is lighter weight and more surface area.

Chamber  First you have to know that there is 223 ammunition, and 5.56.  The 5.56 is loaded to higher pressures for the military.  When a barrel is manufactured the maker cuts the chamber he wants for it.  A 223 chamber is slightly shorter in, and provides slightly more accuracy when used with 223 ammunition.  This can cause a build up of too much pressure in the barrel if 5.56 ammunition is fired in a barrel with a 223 chamber.  If you expect to shoot any kind of surplus ammo, you should make sure you buy a rifle with a barrel chambered to shoot it.  This is slightly complicated by the "wylde" chamber.  This is a compromise between the 223 and 5.56 chambers.  It is intended to allow the user to fire 5.56 ammunition and yet improve on the accuracy of the 5.56 chamber.  This is another option if you intend to shoot surplus ammo.  Want to see the specs on different chambers? Go here: Link to AR15barrels tech page

Twist So, rifle barrels have "rifling" in them.  These are lands (high spots) and grooves (low spots) which run the length of the barrel.  The lands engage a bullet and give it spin as it travels down the barrel, just like a quarterback puts spin on a football.  The rate at which the bullet spins is determined by its speed as it travels down the barrel, and the rate at which the lands twist in the barrel.  The twist is listed as "one in x" were x is the number of inches the bullet must travel down the barrel to complete a single revolution.  Early ARs had 1:12 twist (1 revolution every 12 inches).  However, as bullet design evolved, bullets became heavier and longer.  Longer, heavier projectiles require faster twists in order to stabilize them.  If they do not spin fast enough, they wobble as they go downrange, and you lose accuracy.  If all you want to do is launch 45 grain bullets at prairie dogs with your rifle, you can get away with a 1:12 twist.  Actually, the 1:12 will probably work up to 55 grain bullets.  Most ARs sold these days are 1:9 or faster twists.  The 1:9 will stabilize 55-69 grain bullets, and may sometimes stabilize 75s depending on the rifle.  A 1:8 or 1:7 will stabilize 77 grain and up bullets.  This is important if you intend to shoot at very long ranges where the ballistic coefficient of these bullets is really needed, or if you want to shoot the heavier Black Hills or Hornady ammunition which performs near or at the top for self defense.  You need to decide what you want to do with your rifle from the start so you know what twist you will need.


UPPER RECEIVER

The next thing to think about is the upper receiver.  This is the piece of aluminum that the barrel threads into.  The original design was the M16 which incorporated a “carry handle” with the rear sight mounted at the read of the handle.  This was followed by the “A1” variant which incorporated the forward assist.  The M16 and A1 rear sights require a “tool” (the tip of a bullet will suffice) in order to adjust windage, as a small pin must be pushed down in order to rotate the wheel which adjusts the sight.  Many still prefer this design, as if one is involved in strenuous and harried activity he is not likely to inadvertently move the adjustment.  In addition, this sight was not adjustable for elevation, as the adjustment for sighting in the rifle is made a the front sight post.  The “A2” version is easier to adjust, requiring simply turning the windage knob, but also more likely to be accidentally moved out of place.  In addition, it also incorporates a wheel which lies horizontally below the sight which allows adjustment for longer ranges by turning the wheel and thereby elevating the rear sight.  The “A3” variant is called the “flat top” and is now probably the most common and most versatile.  This has a mounting system milled into the top of the receiver which allows attachment of almost anything you could imagine- including a carry handle, optical sights, back up iron sights, or any air soft junk you could dream of.  In my opinion, unless you are intending to spec out a rifle for a specific “look” there is little reason not to go with an A3 or flat top upper. The “M4 upper is similar to the A3, but it has “M4 cuts” milled into it.  As I understand it, when firing full auto (particularly with a carbine length gas system) it is possible for the carrier to cycle quickly enough to try to strip a round from the top of the magazine before the magazine spring has had time to push the round fully up to be picked up.  This results in the tip of the bullet jamming into the front of the receiver below the barrel’s feed ramps.  The M4 cuts are basically a continuation of the barrel’s feed ramps which extend down into the upper receiver below the bottom edge of the barrel.  They provide a slanted surface which helps start the tip of the bullet in the right direction.  Again, this is primarily a concern if one is shooting full auto, and most would say that M4 feed ramps are not necessary on a semi gun, but this does not stop folks from spending hours extolling their virtues, or getting in heated arguments about them.  Again, Randall has a good thread which shows pictures of these, and what you can and cannot do (basically don’t try to match up a barrel with rifle cuts with a receiver with M4 ramps and you won’t get into trouble) here is a link where you can see Randall's pics of the ramps.

FRONT SIGHT BASE

There is a lot of confusing info out there on this one.  I think I have it right, but feel free to correct me if you know better.  The front sight base (FSB) is an important part of the AR for several reasons:  it serves as the home for the front sight (duh), but it also is the conduit through which the gas is bled off from the barrel to be directed back to the receiver to actuate the bolt and carrier group.  In addition, if you don't have a free float rail, it holds the front of your handguards, as well as your front sling attachment.  First of all, there are "cast" and "forged" front sight bases.  The forged are superior in term of strength, and you will often see this advertised.  The second issue is a little more subtle.  Originally, the 20" barreled rifle used a front sight base which has a platform for the front sight post to thread into which is 1.94" above the top of the barrel.  When the carbine came along, the distance between the rear sight and the front sight (sight radius) became shorter.  This occasionally required the front sight post to be threaded farther out of the base to zero.  Sometimes it would run out of acceptable amount of travel before zero was obtained.  The initial solution was a taller front sight post.  However, when the M4 carbine was created, the decision was made to give it a front sight base which was 1.98" above the barrel, and allow the rifle and barrel to use the same front post.  These taller FSBs are usually (not always) marked with an "F" forward of the roll pin which holds the gas tube in.  This is another selling point which you will see on uppers.  For the most part, "forged F marked FSB" is how they are advertised.  You will often see people say that the F marked base was designed for "flat top" uppers, but I do not believe this is correct for a couple of reasons.  First of all, the resources I checked who seemed to know what they were talking about stated that is was a carbine vs. rifle thing, not a flat top vs. carry handle issue.  Secondly, it is intuitive if you visualize the sight radius that a carbine may require a taller FSB.  Draw yourself a picture showing a horizontal line through the rear sight, and the front sight.  Then draw a second line showing the direction of the barrel.  This line is angled up, so that the bullet travels upward and ultimately crosses the line of sight made by the front and rear sights.  Now draw a second front sight base which lines up with the same line of sight, but with a shorter sight radius.  You will see that the shorter radius requires a taller front sight position in order to achieve the same line of sight, as it is closer to the rear sight.

Because the FSB routes gas to the upper, and does it through the gas tube, the alignment of the FSB to the upper is very important.  If you were to twist your FSB on the barrel, you could decrease the amount of gas going to the upper to actuate the carrier, or you could jam the gas tube in the carrier.  Either of these could disable your rifle.  Thus, pins are often used to fix the FSB into place so it is unable to rotate.  Holes are drilled through the part of the FSB below the barrel, and these holes go through the lower part of the barrel.  Two pins are then driven through both the FSB and the barrel.  The only way to rotate the FSB is now to either shear these pins, or remove them.  The "mil spec" is to use tapered pins.  This means the pin (and hole) is not the same diameter all the way down, but is cone shaped.  This allows a very snug, repeatable fit when you remove and reinstall the FSB.  This is also more difficult to manufacture, so many folks use straight pins.  Does this make a difference in the performance of the rifle?  Only you can decide.  It is very important if you decide to remove your FSB (for example to install a free float forend) that you know if you have taper pins, and you know which way to drive them.  As an aside, I have removed a few straight pins, and bent some Craftsman punches doing it, so there is a surprising amount of force required to drive them out.


BOLT AND CARRIER

The bolt is the piece which picks up the cartridge from the magazine, pushes it into the chamber of the barrel, and then rotates to engage it’s teeth with the barrel extension.  This contains the pressure from firing the cartridge in the chamber until it has decreased to a safe level.  The bolt slides into the carrier, and is held there by the bolt cam pin.  The cam pin slides back and forth in the carrier to rotate the bolt in order to engage the teeth as the carrier comes forward, and to disengage them as the carrier is pushed rearward.  The bolt is the moving part on the gun which takes the most force, and is the most likely to break.  For this reason, after spending most of your money on the barrel, the next place you might consider blowing a few extra bucks is on the bolt.  You can increase your odds of getting a good long life out of your bolt by buying a good quality one.  This gets into the differences between different brands of rifles and components, which we will eventually explore.  Lets say that there was only one company in the world that made bolts, and they sold them to all the different manufacturers.  You would assume that all manufacturers would have bolts of the same quality.  However, this might not be the case.  This is because you can do things to try to find problems with a bolt before it ever leaves your factory.  You can fire a higher than normal pressure cartridge using the bolt, and then send it to be “MP inspected” (Magnetic Particle inspected).  This means that a charge is place on the bolt and then it is surrounded by metal shavings.  The bolt essentially becomes a magnet, and the shavings orient themselves around it.  If there is a flaw in the manufacturing of the metal of the bolt, this produces a disturbance in the flow and therefore a disturbance in the pattern of the metal shavings.  You can now reject the bolt as defective, and improve the overall reliability of your products.  This is one of the main advantages you get from buying products from certain companies.  Some companies MP test all of their barrels, some MP test some from each batch of barrels they make, and some don’t MP test any of them.  The same is true of bolts and carriers.  Obviously this whole process costs money, and thus the more quality control a company does, the more expensive their products become.  Is the difference worth it?  Well, if you spend your days in Iraq, it is clearly worth it, and you would be a fool not to buy the very best you could afford.  If, like me, you spend your days desperately trying to hit that chipmunk which is running around your target 100 yards away it may not be.  My goal in writing all of this is to provide information to people who don’t have a lot of background with the AR so that when they go shopping they can make informed and educated decisions, so decide what you need or want and what you can afford and then buy it.  

Another term you will see in reference to bolts is "shot peened".  As I understand it, this is pretty much just what it sounds like.  The bolt is basted in a process very similar to sand or bead blasting, but instead tiny metal spheres are used.  These impact the surface at a high speed and actually microscopically deform the metal.  The result is like hammering the surface all over.  This results in a bolt which has a very thin surface which is harder and more wear resistant without changing the underlying characteristics of the metal.

Of note, those smart people at Armalite have also figured out another way to increase the reliability of the bolt.  They realized that because the extractor essentially takes the place of one of the bolt lugs, this creates a situation where the force on the bolt is not balanced.  The two lugs next to the extractor take most of the force, because the bolt tilts under the strain from the pressure in the chamber.  For this reason, these two lugs will almost always be the ones which fail.  They figured out that if you shave down the lug directly opposite the extractor so it does not engage the barrel extension, you have again balanced the forces on the remaining lugs.  The say that by doing this, they decrease the force on the two most susceptible lugs by 40% and dramatically increase reliability.  They have, I believe, applied for a patent on this, so they are the only ones who do it.

Now to the lowly carrier.  The carrier is not subjected to the same force as the bolt, and thus is not nearly as likely to break.  The problem you see with carriers involves the extension which comes off the top (the carrier key).  This engages the end of the gas tube.  When the rifle is fired gas is bled off under pressure by the gas block (usually the FSB) and carried rearward by the gas tube.  It is then directed into the key of the carrier to force the carrier rearward.  Unfortunately the carrier key is held onto the carrier by two bolts.  These can easily work loose from all of the constant slamming forward and backward which the carrier does.  For this reason, after they are threaded in, the are “staked”.  This means that they are struck with a punch or chisel in such a way that parts of metal from the carrier key are pushed into indentations made in the heads of the bolts themselves.  This basically deforms and jams the two pieces of metal together in order to prevent the bolts from backing out.  Here again is a source of hours of internet discussion concerning who does a better job staking than everyone else.  Suffice it to say, when you pay more money for your carrier, one of the things you are paying for is someone who should know what he is doing, and has enough attention to detail to do this job right.  This is also something you should inspect when you buy your new rifle to see that it was done correctly.

FIRE CONTROL GROUP (Hammer trigger sear)

Briefly, the standard trigger for an AR is a single stage.  This means that you pull back until the hammer drops, without a significant change in the amount of force you need to apply as you pull back.  This is a fairly simple and bomb proof design.  However, if you really want to be as accurate as you can, you want to hold the rifle perfectly still as you pull the trigger.  The more force it takes to move the trigger, the more difficult it is to hold the rifle still, thus other trigger designs were developed.  The first to consider is a two stage trigger.  This trigger has a small amount of travel which gets taken up with fairly light pressure, and then one hit’s the second stage of the trigger.  Here the force required to move the trigger the remainder of the way to fire increases slightly.  Essentially, you have applied much of the force and accomplished much of the travel of the trigger and you come to an easily recognizable spot in the pull when you know the hammer is about to come down with just a little more force.  This allows you to most of the work in pulling the trigger and then focus on being perfectly still and have the best possible alignment of you sights before pulling the trigger.  Probably the most common two stage trigger is made by Rock River Arms (RRA) and can be had for just under $90 on the Equipment Exchange (EE).  These are fairly good, and can be tuned by a company called WOA to be even better.  There have been some problems with them as they wear in- something involving one of the engagement angles and them going from a two stage to a single stage.  Apparently this can be corrected by someone who knows what he is doing, but that’s all I can tell you about that.  In addition, Bushmaster has I believe recently come out with a two stage trigger, and I believe LMT has as well.  Another option is the Geiselle trigger, which costs considerably more (around $250), and is a bit more complex, but apparently has a great feel and is very high quality.  Supposedly a lot of the high speed low drag (HSLD) guys are going with this trigger and it has a very good reputation.  There is apparently also a new version of the Giselle according to ADCO which is about to be released which will be cheaper and simpler (still around $150 if I remember right).  Also on the high end to consider are triggers by Jewel and Chip McCormick which can be adjusted to release the hammer with very little pressure on the trigger at all.  The older McCormick had a reputation for doubling after a while, but supposedly they have now fixed this.

One thing to remember is that as you get more expensive, and more complex the chances of something going wrong increases.  If you are running around in a combat zone you do not want a delicate target style trigger that can easily malfunction.  The basic trigger is easily the most reliable, and you will find people who have had problems and malfunctions with pretty much all of the upgraded triggers.  I have had great luck with having Bill Springfield tune the stock trigger to bring it down around 4 lbs with his $32 trigger job which can be found listed in the EE here.  This is easily the best money I have ever spent on upgrading an AR.  

So what about all these piston uppers?

In theory the piston upper is a great improvement to the AR design.  The AR is one of few rifles which uses the "direct impingement" design.  This means that gas is bled off under pressure from the barrel and sent back into the action to work the carrier.  This design probably contributes significantly to the accuracy of the rifle, according to many, and keeps the weight down, but has some big downsides.  One is the junk which comes with the gas.  This causes fouling and carbon build up in the action where the critical moving parts are.  In addition it places a lot of heat in this area as well.  With a piston design, the gas vents under the handguards and is used to actuate a piston which in turn drives the carrier backward.  This keeps the debris and heat which comes with the gas out of the inside of the upper, theoretically significantly improving the system.   You hear some folks say that this is the solution to a problem that doesn't exist, but I'll bet if people had a choice between guns with each system and they were equal in  reliability, accuracy, and in cost everyone would go for the piston.  Apparently attempts to "upgrade" to a piston design have gone on for a long time.  There was a drop in design around 20 years ago, which I cannot remember the name of, and there has been a company named ZM weapons making a piston design for quite a while but you don't hear much about them.  Recently there has been a resurgence in interest in pistons.  Patriot Ordinance ?Factory? (POF) has a design, as well as LWRC, and HK. Ares defense has a drop in modification as well.  The POF must be purchased as a complete upper.  I believe the LWRC can be installed by LW if you send your upper to them.  The HK is for the military only right now (unless you have around $4000 for the one what was in the EE recently).  I have seen a few problems noted with the POF design, and many with the Ares design.  One of the main concerns is the force which is placed on the carrier key with these designs.  This has to be very strong to avoid shearing.  

As I said, the theory here is very good, the question is how does the execution work.  There is no question that these systems will be cleaner to run, the concerns are reliability, accuracy and weight.  We will see if these are the evolution of the AR, a temporary fad, or a small market which will parallel the main market at time goes on.


LOWER RECEIVER

There is a great thread concerning lowers that tells more than I  will ever know, so go check it out:  All about Lowers

STOCKS

I am not going to get into this too much, but here are a few basics.  The original stock was the A1 version, and had a  fixed length, and had a relatively short length of pull.  The A2 is slightly longer.  People usually have a preference of one over the other, so if you can try them both with all your gear on which you expect to use with your rifle and see which fits.

Adjustable stocks run the gamut from the simple and cheap to the sky’s the limit.  One thing you need to be aware of is the different sizes of the “receiver extension”, or “buffer tube” which a telescoping stock slides over.  There a “mil spec” diameter (which I believe is slightly smaller) and a “commercial” diameter.  The threads on the two sizes are formed differently.  On the “mil spec” the threads are apparently rolled into the tube, while on the commercial tubes they are cut in.  Apparently, the former is superior.  If this is important to you, make sure you get the “mil spec” version.  I have seen this debated multiple times and have not seen the need to switch all my extensions yet, but I am sure someone will be along to make the case for the milspec version soon.   To me the most important issue here is to make sure that the stock you buy is compatible with the extension you intend to use it with.  

Good basic telescoping stocks include: RRA, Bushmaster, Stag, and others.  More sophisticated versions are made by LMT, Vltor, Magpul, CAA and others.  The best advice I can give here is try to get together with folks who have different versions and try them out, or if no one is around spend some time reading in the forums and asking questions.

FREE FLOAT AND RAILED HANDGUARDS

Probably the first question to ask yourself is do you really need one of these.  If you want a vertical foregrip, or want to mount multiple things on your rifle you will want one of these to hang them on.  Consider, however, that you are adding considerable weight to the rifle, and it is weight which is fairly far from your body.  This will make the rifle handle much differently, and will add to fatigue when shooting for extended periods.  However, the potential to be cooler than anyone else at the range, and to have more toys than all your friends is often irresistible, so here you go:  All about free floats and rails


OPTICS

Optics can give you a considerable advantage on your rifle (an idea our military has bought into full force in the last decade).  When you think about it, using iron sights requires you to line up three points- your rear aperture, your front sight, and your target.  When you use an optic, you only have to line up two points- your reticule (or dot) and your target.  This takes some variability out of the equation, and can make things much faster.  In addition, if your optic provides some magnification, it allows you to gather more information about your target before you choose to shoot it.  With certain reticules, the optic may even assist you in determining how far away your target is, and how much "hold over" you need to hit it.  Zak Smith has posted an excellent article on the three categories of optics one can put on a rifle here which breaks the options into three categories, and I think is an excellent model for considering what kind of optic you want.  First you must decide what you are going to use the rifle for, and then you look at the different brands available in that category.

For all you newbies, there is a guy named "Pat Rogers" who posts around here fairly rarely, who's opinion is pretty highly valued (when you see one of his posts don't make a fool of yourself and tell him how much more you know than he does).  He had some interesting contributions to this thread which were enlightening to me.  You have to read through it all, and pick out what he has to say, but for the most part he advocates red dots for most folks.  At short distances, the red dot is faster than any optic with a reticule because eye relief and parallax are not issues.  If magnification is desired, adding a magnifier adds power without losing that advantage.  The low power variables (the K dot and short dot being what are probably the fastest due to their availability of the daytime visible dot) still have the limitations of eye relief.  There are a lot of options which are becoming available which try to bridge the gaps into an "all purpose optic" and we will see what develops.  For now, I think Zak's model is a good one to consider what you are going to use the rifle for and then look at your options in that category.

"I just want a mil-spec rifle"

So, go talk to your local recruiter.  I learned a lot about this from an article by David Crane in "Combat Tactics" 2008.  Yeah, I know, "Combat Tactics" and "David Crane", I can't believe I even picked it up myself, but if you are interested in this subject, this is the best source I have found.  There is a little information on the Armalite website concerning this here.  The David Crane article, basically says the same thing but with much greater detail about the process.  He apparently was able to sit down with some of the big wigs as Colt, as well as engineers, private and commercial inspectors, and see the whole process close up, and describes it in some detail.  

In a nutshell, "mil-spec" rifles are made based on a "Technical Data Package" which is a closely guarded secret document which belongs to Colt.  This gives the specification for every part on a rifle.  The TDP not only tells the specifications of the part- dimensions, materials to be used, etc, it also specifies how parts are to be tested.

For example, the standard for barrels, is that every one must fire a high pressure round, and then be MPI inspected.  There are specs for testing of every part in the rifle.  The spec might be for individual or batch testing.  Colt and FN must have metallurgists who test samples of every batch of barrels, for example to confirm that the metal the barrel is made of is what the supplier said it is.  This is true of bolts, springs, pins, etc.  Every part has a specification for how it is to be tested, and all testing is documented.  For example, the Crane article says that a lower receiver is inspected for 102 different points.  This is all overseen by government inspectors as well, who can step in and say- "Lets see this particular rifle tested in this way" at random.  

What does all this do for you?  Well, lets say that "company J" forges upper receivers.  One day they make 1000 upper receivers, and happen to ship 500 to FN or Colt for military rifles, and another 500 to Vulcan (just as an example).  The milspec may require that a certain number of the receivers are subjected to destructive testing to confirm that the mix in the alloy was done correctly for the batch.  While doing this, they find that a mistake was made, and the whole lot is rejected.  Meanwhile, Vulcan- the official supplier to the Speshul Forces is busy building uppers out of their receivers.  They can also advertise that they bought their uppers from the same company which supplies the military.  The only difference is the quality assurance which takes place after manufacture.

So, you want to open a company which makes "mil-spec" rifles?  All you need to do is find a copy of the TDP around, hire and train a team of metallurgists, inspectors, and then hire the government to come in and look over your shoulder and confirm all of your test results.  You can readily see that no commercial company has access to the resources necessary to build a "mil-spec" rifle.  Even if you could hire govenment inspectors and get a copy of the TDP, there is simply no way that any commercial manufacturer has the resources to do this- to test every spring, or washer to the level required by the TDP and survive in the AR market.  Based on the way it was described in the article, I would bet that Colt and FN employ FAR more INSPECTORS than most commercial manufacturers have EMPLOYEES.

So is all this testing important?  Well, if your life depends on your rifle, I guess you could argue that it is.  

Well then, what kinds of features/ specs should I look for in my rifle?

We could argue about this all day, but some of the more common specs that are favored include:

MPI, pressure tested, shot peened bolts
Proper staking of the gas key
4150 or CMV chrome lined pressure and MPI tested 1:7 twist barrel
5.56 chamber with M4 feed ramps
Forged FSB (F marked if carbine) with parkerizing under it
Taper pins for the FSB
Mil-Spec sized receiver extention (buffer tube) with staked castle nut


“Yeah, but I really just wanted to know what brand to buy”

Ok, so now we come down to the rubber meeting the road.  I will do my best here, and hopefully folks will correct me where I am wrong.  Also, keep in mind, that not all rifles from any manufacturer are the same.  Colt makes chrome lined M4 barrels, but they also make stainless steel match barrels.  This list may also not be up to date, as folks are constantly changing their products.  You best bet is to decide what features are important to you, then go to the manufacturers' web site and see what they are currently offering.  Given those caveats, here goes:

W

COLT- Colt makes all the M4s for the military.  They also sell rifles to civilians and to Law Enforcement.  The LE models can be purchased by civilians, and they are apparently of higher quality than the “civilian” models.  Colt seems to have the best reputation among folks who train people to use the AR for a living.  This is apparently due to better quality control in the manufacturing process.  You will pay more for these things, and you have to decide if they are worth it to you.  One thing to look out for: some of the civilian Colts have different sized holes where the receivers mate which can making building a gun with them somewhat more difficult if you are mixing brands.

When you pay for a Colt here is what you get:
BARREL:  4150 MP inspected, chrome lined barrels (except match rifles with stainless barrels) with 5.56 chambers and 1:7 twist for the most part with Parkerizing under the FSB  
BOLT/CARRIER:MP tested bolts and carriers
UPPER: M4 feed ramps, taper pins in the FSB
RECEIVER EXTENSION: “mil spec”  

FN- FN makes M16s for the military.  Again, they have very good quality control, but chances are you will never find that out for yourself, as they don’t sell to civilians.  Apparently there were some FN uppers on the market last year, but I have not heard a good explanation as their source.  That “FN” upper that the “Navy SEAL” at the gun show is trying to sell you is more than likely not made by FN.

LMT- Lewis Machine and Tool.  I just learned some interesting history about LMT tonight.  Apparently Karl Lewis was one of the founders of Eagle Arms, which was a retail business run beside LMT until Eagle was sold to Mark Westrom.  Westrom later obtained the rights to the Armalite brand, and combined the two.  This info is from an article by Zak Smith in the 2007 Book of the AR-15.  LMT is also a government contractor, and has good quality control.  LMT apparently makes their barrels in a different way than other manufacturers, which allows greater accuracy.  Most companies buy their barrel the correct size then send them to be chrome lined.  As part of this process, the barrel is etched with chemicals which remove a very small amount of the material.  This makes room for the chrome lining, but is apparently an imperfect process.  LMT buys their blanks from Mike Rock (a barrel maker with a very good reputation for match barrels) and has them made slightly larger to avoid the need for the etching process.  This apparently results in a slightly more uniform process, and better accuracy.  LMT has only entered the commercial market in a big way in the last few years, but now there are multiple vendors on the EE with their products available.  LMT has a good reputation with folks who train for a living as well.

When you buy an LMT you get:
BARREL:  4150 MP inspected, chrome lined barrels (except match rifles with stainless barrels) with 5.56 chambers and 1:7 twist, but without Parkerizing under the FSB  
BOLT/CARRIER:MP tested bolts and carriers
UPPER: M4 feed ramps, straight pins in the FSB
RECEIVER EXTENSION: “mil spec    

SABRE DEFENSE- This is another company which has only recently entered the civilian market.  They are government contractors as well, and are ISO 9001 certified.  I don’t know what that means, but I understand that it indicates that their manufacturing standards must meet a very high level in order to maintain their certification.  They have very recently received a contract to manufacture M16A4 rifles for the military, and so join FN and Colt as the only three companies currently building an M16 (or M4) for the military.  Apparently, their primary defense contracts previously have involved rifle barrels, and they are very good at manufacturing them (again, one of the few companies to make their own).

When you buy a Sabre you get:  
BARREL:  4150 MP inspected, chrome lined barrels (except match rifles with stainless barrels) with 5.56 chambers and 1:7 twist, with parkerizing under the FSB  
BOLT/CARRIER:I a unsure about MP testing on bolts and carriers
UPPER: M4 feed ramps, I am unsure about pins in the FSB
RECEIVER EXTENSION: Not sure  

NOVESKE  This is a fairly small, high end company, which has made a reputation for itself quickly.  They make their own barrels (as above, a rarity in the business) and offer some products which are not available anywhere else.  The offer barrels with double thickness chrome lining, which are reputed to be more durable.  They also offer barrels made of M249? machine gun blanks, which apparently is a better material than the 4150 used in an M16 (or are at least marketed as such).  I think of them as almost a "semi custom" manufacturer, who offers stuff you can't find elsewhere, but which you must be willing to pay for.

BARRELS: As above
BOLT/CARRIER:  Bolt is MP inspected, shot peened, not sure about carrier
UPPER: M4 feed ramps
RECEIVER EXTENSION: Mil spec

CMMG  Another fairly recent company, which has a pretty good reputation, but some detractors who mention problems with barrel concentricity, and an old issue involving some kind of flash hider threading mistake on one rifle.  As someone once put it, CMMG is the “Burger King” of upper manufacturers- you can have it your way.  They offer a dizzying array of configurations.  They offer stainless and chrome moly barrels in pretty much every profile and length.  There have been a few recent threads concerning customer service (or a lack thereof) so you might want to do a search and see what the most recent info is before you order.

When you buy CMMG, you get:
BARREL:  4150 MP inspected, chrome lined barrels (except rifles with stainless barrels) with 5.56 chambers and 1:7 twist, with parkerizing under the FSB  
BOLT/CARRIER:Via the grapevine (below) bolts are apparently MP tested (?batch or individual?), unsure about carriers
UPPER: M4 feed ramps, taper pins in the FSB
RECEIVER EXTENSION: I think both types are offered

ARMALITE  Armalite is a great company.  There are some companies which make (build for the most part) AR15s, and then there are companies which actually advance the AR platform.  Armalite is one of the latter.  I think that this may be because the owner was an army ordinance officer and a shooter, and has a vision for improving things.  Want to learn some stuff about ARs?  Go to the Armalite library and look around.  As noted above, Armalite developed the midlength gas system, as well as their own unique and simple bolt improvement.  

When you buy Armalite, you get:
I could use some help here from folks, as I don't know their products so well:
BARREL:  4140 in the past, but now apparently switching to 4150, I am not sure about MP inspection, chrome lined barrels with ?5.56 chambers and 1:9 twist, I am not sure about parkerizing under the FSB  
BOLT/CARRIER:I am not sure about MP testing of bolts and carriers
UPPER: M4 feed ramps, straight pins in the FSB
RECEIVER EXTENSION: milspec

STAG  Stag is the retail side of CMT which stands for Continental Machine and Tool.  CMT makes a lot of the parts that other manufacturers use to build their rifles.  Only in the last few years have they started selling directly to the consumer through the Stag brand.  If you want a left handed AR15 they have what you want.  

When you buy a Stag, you get:
BARREL:  414?0 I believe, non MP inspected, chrome lined barrels with 5.56 chambers and 1:9 twist, I am not sure about parkerizing under the FSB  
BOLT/CARRIER:I believe they MP test some bolts which are sold specifically as "MP tested", but not all bolts.
UPPER: Rifle style feed ramps (not M4), and I am told taper pins which are inserted the opposite direction of most others in the FSB
RECEIVER EXTENSION: mil-spec

Bravo Company Manufacturing (BCM)  I did not initially include them because I have wanted to buy one of their uppers for a long time and they have not had them in stock for many months.  BCM is a business which has a very good reputation on the board for selling quality stuff and having good service.  They offered their own line of uppers for a while which were very high quality.  It looks like a lot of their business now involves LMT products, and I wonder if they are just too busy to work on their own uppers.  They are a good source for BCGs which have shot peened and MP inspected bolts, but then LMTs are about the same price from them as well.

If you can find a BCM upper, you will get:
BARREL:  4150 MP inspected, chrome lined barrels with 5.56 chambers and 1:7 twist, with parkerizing under the FSB  
BOLT/CARRIER: MP testing on bolts, I am not sure about carriers
UPPER: M4 feed ramps, I believe straight pins in the FSB
RECEIVER EXTENSION: I believe mil-spec, but am not sure

RRA This is a company which is again only a few years old.  Their claim to fame is having won a contract to supply rifles to the DEA.  They have a pretty good reputation for "fit and finish", meaning appearance of the upper and lower receivers, as well as a tight fit between the receivers.  This may or may not be important to accuracy (not very important if it is).  

When you buy RRA you get:
BARREL:  4140 NON MP inspected, NON chrome lined barrels  with 5.56 or Wylde chambers and 1:9 twist I am unsure about parkerizing under the FSB FOR THE MOST PART, HOWEVER, RRA now offers chrome lined 1:9 and 1:7 barrels if you specify them
BOLT/CARRIER:I do not believe they MP test bolts and carriers
UPPER: "Dremeled" M4 feed ramps, which means the feed ramps are cut in by hand after the barrel is installed, instead of being manufactured into the receiver, and  straight pins in the FSB
RECEIVER EXTENSION: commercial

BUSHMASTER  Bushmaster has been around longer than many of the "new comers".  The old guys remember when your main choices were "ABC" meaning Armalite, Bushmaster and Colt.  They were recently purchased by a big conglomerate which also purchased Remington if I remember correctly.  Bushmaster has sold a few rifles to the military, mainly for testing, but is not a significant supplier.

When you buy a Bushmaster you get:
BARREL:  4150 chrome lined barrels, which I believe are "batch tested" with MP inspection, with 5.56 chambers and 1:9 twist I am unsure about parkerizing under the FSB FOR THE MOST PART, although I believe they now are offering some 1:7 twist barrels
BOLT/CARRIER:Per the BM catalog carriers are MP inspected, not sure about bolts
UPPER: Rifle type (No M4 cuts) and  taper pins in the FSB
RECEIVER EXTENSION: commercial

Charles Daly   As I understand it, these guys are mainly importers.  They have a reputation for low end shotguns, but have started selling ARs in the last year.  I have to hand it to them, as they came here first, and posted some threads saying: "What do you guys want", and then seemed to actually listen to the answers before they started marketing product.  As a result, they came up with some pretty good stuff right off the bat.  They don't have a track record yet in terms of customer service, or reliability, but I have been impressed with their business approach so far, and they claim to offer a lifetime warranty.  We will see how things go for them.  They offer a "commercial" version, and a more "mil spec" version.  The latter includes:
BARREL: 4150 chrome lined, 5.56, 1:7
BOLT/CARRIER:?
UPPER: M4 ramps, F marked front sight base
RECEIVER EXTENSION: Mil spec

Smith and Wesson  A company which needs no introduction, they only recently entered the AR market, but are developing a good reputation.  When they first started selling ARs, apparently most of their work was done by CMT, although they apparently have been doing more and more in house.  Early lowers were not compatible with P mags, but apparently this has been rectified.
BARREL: 5.56, Chrome lined 4140
BOLT/CARRIER:?
UPPER: ?M4 cuts?
RECEIVER EXTENSION: Mil spec

DoubleStar Arms   This is a sister company of J&T Distributing, which sells only parts and kits, while DoubleStar sells complete rifles.  According to an article in the April 2007 Shot Gun News, by one of my two favorite AR writers (David Fortier) they have been around since 1999.  Other than this, I don't know too much about them.
BARREL: 41?0, 1:9 non chrome lined standard, chrome lining available
BOLT/CARRIER: ?
UPPER RECEIVER: I see no mention of M4 cuts in Fortier's article, or on their site
RECEIVER EXTENSION: ?

Del-Ton  I have not dealt with this company, but they are a site sponsor, and are popular for their good pricing and service.  According to their website, they offer complete DPMS rifles, as well as some of their own products.  You can order a kit through them with many different options, including different barrels, handguards and stocks.  It looks like they offer at least one 16" upper which has the following:
BARREL: Wilson, 1:7 Chrome lined, 5.56
BOLT/CARRIER: ?
UPPER RECEIVER: M4 ramps, F marked FSB
RECEIVER EXTENSION:?

Olympic Arms   This company has been around for a long time as well.  I believe they are one of the few companies which manufactures their own lower receivers, which has led to some out of spec problems in the past.  They also make their own barrels, including some stainless "Ultramatch" barrels which have a very good reputation for accuracy.  Unfortunately some of their other parts are hit and miss.  Overall they have some supporters and a fair number of detractors on the board.  I lost respect for them myself when I bought an upper from them 8 years ago which had been machined incorrectly and then overbored and an insert place in the front pivot pin hole to bring it back to spec.  I think most other manufacturers would not have tried to sell one of those as a "normal" receiver.

When you buy an OA you get:
Someone want to help me out with specs?  Thanks

DPMS (Defense Procurement Manufacturing Systems) is a company which has been around for a while.  They have a decent reputation with a few exceptions.  One thing that comes up frequently is that their bolt seem to break at the cam hole pin more often than other brands.  There is also an issue with their lower parts kits in that the trigger and hammer pins are oversized and can be a royal pain to install.  A lot of companies use their lower parts kits to put together "whole rifle kits" which you can add your stripped receiver to, so if you are cursing your hammer/trigger pin because it won't go in it probably came from DPMS.  Get out some fine sandpaper and chuck the pin in a drill and take a little off.  DO NOT screw up your lower trying to hammer it in.

When you get a DPMS you get:
BARREL:  4140, non MP inspected, chrome or non chrome lined barrels I am not sure about chambers I believe most have 1:9 twist, I am not sure about parkerizing under the FSB.  They also offer many other calibers, I am told, including: .204 Ruger, .22LR, .223 Remington, 5.56x45mm, 7.62x39mm, 6.8x43mm SPC, .243 Winchester, .308 Winchester, .260 Remington and .300 Remington SAUM.
BOLT/CARRIER:I do not believe they are MP tested
UPPER: Rifle style feed ramps (not M4), and I believe straight pins in the FSB
RECEIVER EXTENSION: I believe commercial

M&A Parts and Model 1 Sales   I lumped these two together because they are fairly similar.  However, as pointed out on the second page of the thread, they are distinct companies.  I believe that the owners are actually relatives by marriage, or something like that.  They both supply low cost "kits" which provide an assembled upper, and all the parts to finish a stripped lower.  In addition they sell uppers and some accessories.  These are an inexpensive way to build a rifle, but probably do not have the quality control that the other companies mentioned above have.  Some folks have great luck with them and are very happy.  There was an infamous "Darth Vader" thread that went around for a while which I believe dealt with the owner of M&A going nuts at some gun show at some guy and being put in his place, so customer service might be an issue with M&A specifically, and this might be a reason to go with Model 1 Sales.  Also, M&A claims that their uppers are assembled by LMT (Scroll down to the "who makes our stuff" heading ) although I think it would be safe to assume that the parts they supply to LMT are not subject to the same quality control as LMT branded parts are.
When you buy an upper from these guys you get:
I don't know, anyone want to help me out?

VULCAN/HESSE/BLACKTHORNE  These guys have been around a while to.  They have several names because their products are so bad they have to come up with a new brand name every now and then to try to fool people into buying their products.  I am not sure where their products come from, but based on their reputation and cost, many are probably made in China.  They use inferior materials, and I don't know and am not interested in the specs on their rifles, as you should not buy one.  The best part about these guys are the material they provide for online quips.  Two of my favorites are:  "Friends don't let friends buy vulcan/hesse/blackthorne", and "Vulcan, guns of the "SPECIAL" FORCES (the ones who rode the short bus to school)."

What does all this come down to?

You have to decide what you want and how much you want to pay for it.  Can you buy a Colt and get a lemon?  Yes.  Can you buy an M&A kit and get a great rifle?  Yes.  When you pay more for parts you are paying more for something which is MORE LIKELY to perform well.  The extra you pay for the Colt makes it LESS LIKELY that you will have a problem, but does not make it impossible.  The smaller amount you pay for one of the cheaper uppers means less quality control and makes it MORE LIKELY that you will have problems.   If you are a contractor or SWAT cop going into dangerous places, you should spend as much as you can afford because the price of a part failure can be your life.  In addition, when you pay more for higher quality raw materials, you will likely get a longer life from them.  If you are intending to attend courses which teach you to shoot (we all should), or to compete in three gun competition or you like to put many hundreds of rounds downrange when you go out, you will likely start to stress your rifle more and you will probably see the benefit from the extra $ you put into your gear. To me, putting more money into quality components is getting easier and easier.  When you consider that 1K of Wolf ammo is going for over $200 these days, putting an extra $200 into a rifle which will probably last the rest of your lifetime is a no brainer.  That said, we don't all need Colts.  Most of the companies above provide very good products which will meet the needs of most users.  Buying a decent product and then spending a lot of time using it is the best way to find out if it is reliable, as well as being ready to use it if the need ever arises.  One of the great quotes which floats around about this is "Its the Singer, not the Song".  Put a Vulcan in the hands of some HSLD guy, and an HK 416 in my hands and put us up against each other, and I can tell you who will win every time.  That's my $.02 at least.

Why does everyone tell me to build my own rifle?

Because ARs are like legos- you can spend hours taking them apart and putting them together in different ways.  There are a few other good reasons.  One is that the federal govt taxes complete rifles with something called a "Federal Excise Tax" which I believe is 11% (by the way, I never realized that there was a FET of 11% on ammo as well until I looked this all up).  This means if you buy a complete rifle you are going to pay this cost on top of what you would pay if you simply bought the parts and put them together.  Because the receiver is the serial numbered part, it is the only part you have to buy though a FFL licensed dealer.  There are several ways to go.  You can buy a "stripped lower" and install a "Lower parts kit" which will include all of the parts inside the lower, and the handgrip, (but not the stock) and then add an "upper" and stock to it.  This is a very easy process well within the reach of any man who has a current man card.  You can also find "complete rifle kits" from most manufacturers which include all the parts you need except the lower.  There are a few tricks to putting a lower together, and buying a video will clue you into them, but you can probably figure it out yourself with an exploded parts diagram if you are pretty mechanically inclined.  I put two together on my kitchen floor in about 30 minutes the other day using only a punch, and allen wrench, and a wrench to tighten the receiver extension castle nut.  The second way you can go is to buy a "complete lower" which includes the lower receiver with the parts kit and usually the stock already installed. Then all you need to do is install an "upper" by pushing the two pins home.  When you start looking at uppers, most of the time you will find them sold fully assembled.  This is handy, because you have to have a few specific tools to assemble one yourself.  This is not difficult, and one of the beauties of the AR platform is that you don't have to headspace the barrel yourself.  You can probably buy the tools to do this yourself for less than $100.  However, if you buy a complete upper, you don't have to mess with this.  Be careful when you price uppers.  Sometimes you are buying an upper which includes the Bolt and Carrier (BCG) and sometimes you are not.  Sometimes you are getting the charging handle, and sometimes you aren't.  If you look and see that an LMT upper goes for $485, and that a RRA upper goes for $450, you might think that you are only going to pay $35 more for the LMT.  However, the RA comes with the BCH but the LMT does not.  Expect to pay $100-$130 more for your BCG.  Pay attention to the details when you order so you don't end up frustrated.  I think that at least putting together a lower parts kit is very useful knowledge on how everything works.  As you learn more, and develop preferences, you will be able to build exactly the rifle you want and make changes yourself as new products become available.  Do yourself a favor, and buy a video and at least learn how everything works.

How do the companies rank?

Boy, did you open a can of worms there.  This is the subject of endless debate, and heartburn around here.  I have decided not to get caught up in it other than to say that some of the very best are:

NOVESKE
COLT (may be less than, equal to, or better than Noveske, depending on whose talking)
LMT/ SABRE  

Most would agree that these companies build some of the highest quality ARs, and each will have its' fans arguing the order.  These are the ones who have the most of the "desirable features" listed above if you are looking for a "military spec style rifle".  Do you need one of them?  That's up to you, your budget, and your situation.


As I say above, you would be better off deciding which features are most important to you, and then seeing which manufacturer offers them, and avoiding the whole "brand ranking" stuff altogether.

Also, keep in mind, that when you start comparing brands, your opinion and mine are not all that important (other than customer service), as we see a very small sample size.  To really see trends in reliability/ quality you need to see many many rifles being stress tested.  This is why, to me, the opinions of guys like Larry Vickers, or Pat Rogers are valuable.  These guys see literally thousands of rifles being put to the test yearly, and when you see a post with someone with experience like this, you should take note.

this thread should be tacked.  However, even if it was, there would still be the same hundred questions on the same stuff covered in your write up.
BTW, Good job.

Much better than I expected it to be.

About time someone did this. Good job.

There's some really good info in that post.
Now we just have to wait for 18 pages of bitching, moaning, and infantile squabbling followed by a lock before this gets stickied.
Good post Jus.

You have the approval of the trifecta.

Thanks for the kind words, guys.  I could use some help with proofreading- specifically with the different brands and what they offer.  Also, if anyone wants to add more brands, post the info and I will include them.

Tell me about slings and pistol grips, those are the really important topics, jeez......

J/k, great post, lots of info.

"Can we get a sticky on aisle 2?"

Quoted: Thanks for the kind words, guys.  I could use some help with proofreading- specifically with the different brands and what they offer.  Also, if anyone wants to add more brands, post the info and I will include them.

Quoted: ....STAG Stag is the retail side of CMT which stands for Continental Machine and Tool. CMT makes a lot of the parts that other manufacturers use to build their rifles. Only in the last few years have they started selling directly to the consumer through the Stag brand. When you buy a Stag, you get: BARREL: 414?0 I believe, non MP inspected, chrome lined barrels with I believe 223 chambers and 1:9 twist, I am not sure about parkerizing under the FSB BOLT/CARRIER:I believe they MP test some bolts which are sold specifially as "MP tested", but not all bolts. UPPER: I believe M4 feed ramps, and I believe straight pins in the FSB RECIEVER EXTENSION: I believe both commercial and milspec are offered

Good job.

Just a note on the STAG info:
They have 5.56 chambers.
The upper rec and bbl have the "standard" rifle feedramps, not M4, and the FSB is installed with tappered pins. They are just installed from the opposite side, right to left, instead of left to right.

My RRA A2 20"er also has the tappered pins holding in the front site base.

Very nice and helpful write up. I wonder if anyone will actually read it before they ask "what should I buy?".

By the way, can you include Bravo Company?

Threads like this make me wonder why ar15.com doesn't have a wiki that we could all contribute to.

Nice writeup.

Great post!

Great info.

Absolutely sticky material!!

Guys,  Ijust found this site. My friend has a Vulcan AR 15 for sale, is it a good deal and should I buy it?????

My co-worker was told by CMMG on Friday 9/16/07 that their bolts were MP tested.  Good company to deal with from the LE side.

Quoted: Guys,  Ijust found this site. My friend has a Vulcan AR 15 for sale, is it a good deal and should I buy it?????

 Vulcan IS the weapon of the special forces. You should offer him $2000 for it.

Tag for later.

Page 20 bushmaster catalog carrier,s are magnetic
particle inspected for cracks or flaws.

hanks,Sonnytoo

AFAIK as a dealer..Stags factory assembled carbines all come with milspec reciever extensions (buffer tubes). If you run into a Stag with a commercial tube it was more than likely gunshop or home assembled.

+1 for an awesome post.  great information here.

Quoted: Page 20 bushmaster catalog carrier,s are magnetic particle inspected for cracks or flaws.

I never saw that before, will change the info,  I wonder if that is batch tested or each individual one it tested?  I also updated the other info posted.

Thanks all

Made me want to buy another, Good work. I'm play'in with mine now. Wow!

Good post.....should be tacked........

CMMG uses taper pins in the FSB.

i cant stand vulcan after buying one of their 50 cals. the gun was a safety hazzard and they didnt care to help me out. worst customer service ever. and im a dealer. what kind of service do you think their going to give the consumer. ive also heard from people that every time word gets out that their crap they just change their name, and start over.

Juslearnin - Where have you been all of my life??  he
Thanks again.

-huskAR

great post- juslearnin,

Thanks for the corrections- and keep them coming please.  I am sure there is still quite a bit which is not correct about the manufacturers, as well as some big holes about specific ones.

You  lumped all SBRs together.  You said once you go under 14.5" you can go as short as you want.  Total over simplification.  This is the length where minute differences become much more of a big deal than the 16"-18" differences.  Certain rails, suppressors, etc cant be used on some 10.5" barrels but work fine on 11.5" and up barrels.  The wounding patterns of 12.5", 12.0", and 11.5" barrels can be up to twice the range of 10.5" or shorter barrels.  The 13.7" with use of the bulgarian style flash hider was ignored.  Many other aspects ignored as well and this is the MOST critical of decisions... what barrel length, material type, and chamber when you want to go under 14.5" since velocity conc3rns are much greater if you have any interest in terminal ballistics at all.

Under twist you seem to say the only reason to use the heavy ammo is to shoot at very long ranges.  You ignore the fact the best self defense rounds are heavy OTM rounds.  This would be why you want them in a SBR... a barrel length NOT used to shoot long ranges.

You ignored fluting in the barrel section completely.

You stated that stainless was corrosion resistant and was like hard chrome.  416 is not very corrosion resistant at all and hard chrome will surpass bare 416 by over 2 to 1 in the amount of time it takes to corrode in salt spray testing.  Stainless is not very stainless in gun barrels.  It cant hold a candle to hardchrome for corrosion resistance.

You ignored the effect of a target crown on a threaded barrel vs just a flat interface between the rifling and the front of the barrel.  Target crowns work on threaded barrels too and you WANT this.  Very few manufacturers offer this.  A good reason to cut a 16" to a 14.5" would be to get a target crown on your barrel.

You lie about triggers.  You state the more complex and expensive triggers are more likely to fail.  You try to act like the $90 RRA 2 stage which has the most reported failures on this site is more reliable than the Geissele which is $275 and has set screws yet is the most reliable aftermarket 2 stage you can get.  Please cite me a failure of the GA trigger.  I have never seen one.

You totally skipped over the piston driven guys POF/LWRC and the piston kit in the Ares system.

Sounds about as accurate as most gun rags.  Some good info and some total BS thrown in for good measure.  I give it a B- so far.  I hope you keep working on it.

A B-?  Man you're tough!  Can I do some extra credit to get it up?  Well, Devl- you write me a good section on SBRs I'll include it.  In my mind SBRs are a fairly small, and as you point out specialized area of ARs.  These are not areas where I have much expertise, but obviously you do.  My intent here was not to write a comprehensive and exhaustive description of everything which goes into an AR, but to give the basics.  I could be wrong, but I don't think most newbies are going to buy a SBR for their first rifle, or spend $250 on a trigger for their first rifle.  These are both specialized pieces of equipment used by people who already know a lot more about ARs than I do and don't need a tutorial.  I did not intend to imply stainless was as durable or resistant to corrosion as chrome, and I will go back and look at that section to try to make it more clear.  I also cleaned up the trigger section- adding a note about RRA two stages having probs and praising the Geiselle a little .  I also added a section on fluting, as well as piston uppers.  As you suggest, I will keep working on it.

Great thread, great info.  Wish I'd have had something like that when I started looking.

The only thing I'll add, is that for a newbie, handle as many as you can before buying.  Don't rely on pics and what you read on the internet.  You may find (like I did) that you really DO NOT want that HBar dissipator, once you handle it.  There is a big difference in barrel profiles.  Educate yourself on that to avoid making a mistake, and by educate, I mean hold and fondle as many rifles with as many profiles as you can.  Some will just "feel right" to you, and others will not.  I'm big into that, if a rifle does not feel right in my hands I don't want it, because I'll probably never grow to really like it.

I ended up with a Bushmaster Superlight and I'm glad I did.  Most everything out there locally is either HBar or M4 profile.  Once I held a Superlight, I knew that was the one for me.

NICE WORK!!

As a note on steel. The first two numbers (i.e. the "41" in "4140") denote the series of steel, so both 4140 and 4150 are chrome-moly (Chromium Molybdenum) steel. The second two numbers (i.e. the "40" in "4140") denote the carbon content in the steel, which means that 4150 steel will typically be harder than 4140 as it has more carbon. CMV is chrome-moly w/ vanadium; vanadium is added to improve abrasion resistance in the steel.

This is just off the top of my head so you might want to check it.

IMHO, combat weapon or not, everyone needs a good BUIS, you never know. I'll review the ones ive'd used and post it in a bit!

Really nice write up.  I wish I could have gotten this type of response when I got my first AR.  There is an encyclopedia of information that could be added, but for a simple "So You Want an AR" or "Living with BRD" pamphlet, this is spot on.

I also liked DEVL's discussion of shorter barrels.  Never saw it put that way.  DRINKS ALL AROUND!  Honestly, this should be tacked.  

R/
Mike

Quoted: great post- juslearnin,

+1

mods, pls tag this!

For anyone who wants to add info or corrections, I will be traveling for the next 10 days and may not be able to update the original post.  I will try to get online somewhere and do it if I can, but may not get the opportunity until then.  Thanks.

Just wanted to bump this so newbies can find it.

Thanks for the bump.  Brand new here and looking to build my first AR.  Thanks for taking the time to do this.  VERY informative!!!

BTW, which lower should I buy?  JUST KIDDING!!!!

So what AR should I buy?

Armalite is making the change to CMV steel for barrels.

Bravo and NOVESKE should be right under LMT

Quoted: You  lumped all SBRs together.  You said once you go under 14.5" you can go as short as you want.  Total over simplification.  This is the length where minute differences become much more of a big deal than the 16"-18" differences.  Certain rails, suppressors, etc cant be used on some 10.5" barrels but work fine on 11.5" and up barrels.  The wounding patterns of 12.5", 12.0", and 11.5" barrels can be up to twice the range of 10.5" or shorter barrels.  The 13.7" with use of the bulgarian style flash hider was ignored.  Many other aspects ignored as well and this is the MOST critical of decisions... what barrel length, material type, and chamber when you want to go under 14.5" since velocity conc3rns are much greater if you have any interest in terminal ballistics at all. Under twist you seem to say the only reason to use the heavy ammo is to shoot at very long ranges.  You ignore the fact the best self defense rounds are heavy OTM rounds.  This would be why you want them in a SBR... a barrel length NOT used to shoot long ranges. You ignored fluting in the barrel section completely. You stated that stainless was corrosion resistant and was like hard chrome.  416 is not very corrosion resistant at all and hard chrome will surpass bare 416 by over 2 to 1 in the amount of time it takes to corrode in salt spray testing.  Stainless is not very stainless in gun barrels.  It cant hold a candle to hardchrome for corrosion resistance. You ignored the effect of a target crown on a threaded barrel vs just a flat interface between the rifling and the front of the barrel.  Target crowns work on threaded barrels too and you WANT this.  Very few manufacturers offer this.  A good reason to cut a 16" to a 14.5" would be to get a target crown on your barrel. You lie about triggers.  You state the more complex and expensive triggers are more likely to fail.  You try to act like the $90 RRA 2 stage which has the most reported failures on this site is more reliable than the Geissele which is $275 and has set screws yet is the most reliable aftermarket 2 stage you can get.  Please cite me a failure of the GA trigger.  I have never seen one. You totally skipped over the piston driven guys POF/LWRC and the piston kit in the Ares system. Sounds about as accurate as most gun rags.  Some good info and some total BS thrown in for good measure.  I give it a B- so far.  I hope you keep working on it.

HARSH but TRUE

Quoted: DPMS (Defense Procurement Marketing Systems Manufacturing Services) is a company which has been around for a while.  They have a decent reputation with a few exceptions.  One thing that comes up frequently is that their bolt seem to break at the cam hole pin more often than other brands.  There is also an issue with their lower parts kits in that the trigger and hammer pins are oversized and can be a royal pain to install.  A lot of companies use their lower parts kits to put together "whole rifle kits" which you can add your stripped receiver to, so if you are cursing your hammer/trigger pin because it won't go in it probably came from DPMS.  Get out some fine sandpaper and chuck the pin in a drill and take a little off.  DO NOT screw up your lower trying to hammer it in. When you get a DPMS you get: BARREL:  4140, non MP inspected, chrome and non chrome lined barrels I am not sure about chambers They offer .204 Ruger, .22LR, .223 Remington, 5.56x45mm, 7.62x39mm, 6.8x43mm SPC, .243 Winchester, .308 Winchester, .260 Remington and .300 Remington SAUM. chambers I believe most have 1:9 twist, I am not sure about parkerizing under the FSB   BOLT/CARRIER:I do not believe they are MP tested UPPER: Rifle style feed ramps (not M4), and I believe straight pins in the FSB RECEIVER EXTENSION: I believe commercial

YOU MUST HAVE ALOT OF FREE TIME ON YOUR HANDS! VERY nice job!! Basically what I tell those who ask me about AR's is, "Save up til you can afford COLT/LMT, their Kool-Aid is the BEST!!

Not bad, not bad.

To me the best is when you start assembling your own or in my case where I live rebuilding my factory pre-bans.Every manufacturer is just an assembler even the few who make some of their parts in house..and with that hand picking quality  parts to come together as a rifle is the best and lots of times equal to what it costs for a factory rifle.

Wow, that is awesome, that must answer 20% of all the posts here.

Quoted: NICE WORK!! As a note on steel. The first two numbers (i.e. the "41" in "4140") denote the series of steel, so both 4140 and 4150 are chrome-moly (Chromium Molybdenum) steel. The second two numbers (i.e. the "40" in "4140") denote the carbon content in the steel, which means that 4150 steel will typically be harder than 4140 as it has more carbon. CMV is chrome-moly w/ vanadium; vanadium is added to improve abrasion resistance in the steel. This is just off the top of my head so you might want to check it.

That pretty much sums it up.  I spent 5 years in a metallurgy lab and the "40" and "50" are definitely the carbon content which determines hardness.  I believe "40" means .040% carbon, for example.  (My decimal point might be off one place--it was over 10 years ago when I left that career.)

Just a note:  those numbers are only nominal and, just like rate of twist, they may actually vary quite a bit from batch to batch.  For example, one batch of 4140 may have .044% carbon and a batch of 4150 may actually have .046%, depending on the spec.  Carbon content is very difficult to control in steel because it tends to burn off rapidly while the steel is molten.  Extra carbon is put in knowing that much of it will "burn off".

When making steel certain "burn-off elements" (such as Aluminum and Titanium, IIRC) are thrown in the pot intentionally to burn up the oxygen in the metal and thus reducing porosity.  This is why you should avoid breathing the fumes from a foundry.

This concludes our metallurgy lesson for today.

P.S.  Excellent write-up OP!

Great job.

My only comment is that I would separate M&A parts and Model 1 Sales. Even though they may have been owned by relatives (brothers?), I believe they are run as compeltely separate companies - epseically since Model 1 Sales moved to Texas a few years ago.

I mention it because I have generally heard pretty bad things about M&A Parts, but have had nothing but good experiences with Model 1 Sales myself (and have heard that same from almost all other people that have bought from them in the past few years).  In recent years, M1S has had really good quality, and the complaints you hear about their stuff is generally either from people that bought stuff from them many years ago, or people complaining about how their lower parts kits (trigger and small parts) can be a little rough.  However, as a source of uppers, Model 1 Sales actually provides decent quality at a very low price.

I'm not advertisting for them or anything - I'm just saying that I think it may be unfair to Model 1 Sales to lump them in with M&A Sales.  

As a newbie, I will definately be consulting this information for my first build.

Thanks all for taking the time to create/maintain the accuracy of this thread.