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Posted: 2/25/2006 5:45:54 AM EDT
[Last Edit: 2/26/2006 11:13:34 AM EDT by KorpiszZ389]
OK guys, I'm not exactly sure how these things work but I have a basic idea. I still fail to see why they are supposed to be more reliable than a standard gas system. I haven't been around very long, but I've yet to see a problem with a standard gas system. Is the piston just a solution looking for a problem? With a standard gas system, once the gas enters the port in the top of the barrel, goes through the tube, and cycles the bolt carrier, the excess is dumped into the receiver, right? Well what happens with the piston uppers? I've heard gas is released under the handguards, is this true?

I've been hearing a lot of hype about it lately, especially after SHOT. I am thinking about getting one of the Colts when they come out in 14.5" for my 6921 SBR for CQB work and maybe eventually a 3 gun match. Do you think it is worth it or should I just stick with the standard system? I want this gun to be the absolute tops in reliability, no exceptions!
Link Posted: 2/25/2006 5:50:39 AM EDT
I think of it this way. How long has the U.S. Military been using the M16? If the piston stuff was all it is cracked up to be, why is it just now comming out ina big way? You can't tell me technology is changing, because gas piston systems have been out forever...

I feel it's just another guy trying to mak a buck with a new idea. Some fish will bite, others won't. It's just not the right lure to catch me...
Link Posted: 2/25/2006 5:56:17 AM EDT
Link Posted: 2/25/2006 6:05:53 AM EDT
The direct gas system works. There is no doubt about that. It is just alot more sensitive to different ammos, it blows dirty fouling gas right into your bolt carrier, which in turn gets your chamber filthy. The direct gas impingement also heats the bolt carrier group very hot with all of those gases. This weakens extractor springs,ejector springs and eventually will weaken all of the metal components over time. Heat is an enemy to mechanical parts.

This is why I beleive in the gas piston. It solves these issues. It keeps the upper reciever parts including the bolt carrier group and chamber much cooler and cleaner.

Pistons are far less sensitive to weaker ammos, different buffer weights and buffer spring tensions. Through my testing ( very unscientific) that when fine tuning my direct gas AR's with different buffers and springs, it can make or break them. Different barrel lengths, when matched up to the wrong buffer weights, using different ammos can ruin a direct gas gun.

My piston AR shoots any ammo, with any weight buffer or spring all of the time. It does this without even getting the bolt carrier group dirty or hot.

The piston does add some weight and more components to the mix, but to me it is well worth it. Especially for a foot soldier who needs his weapon to run.
Link Posted: 2/25/2006 6:17:00 AM EDT
Link Posted: 2/25/2006 6:21:56 AM EDT
One of the first FN A2 uppers.
Admittingly the old magazines were a large part of the reliability issue but
a piston op AR would have mades things much nicer. Cleaner running , less heat, etc.

Maybe its a jumping on the bandwagon thing, but Colt, HK, LW and POF are seeing the light. The US military's next issued weapon will be piston driven . That should be proof enough.
Link Posted: 2/25/2006 6:28:17 AM EDT
reliability = quality ammo + quality gun.

Yes, piston guns take more tolerance to different ammo. If you use quality ammo, I don't see any big issue for gas guns.

The major drawback of m16/m4/ar15 is on its magazine design rather than its action.

Remember the benefits of the gas guns - light weight, light recoil, and less moving parts as you shoot. That is why people alway appreciate the accuracy of AR15.

I like gas guns and like piston guns too. They are different breed. They perform good result if you know how to operate them.
Link Posted: 2/25/2006 6:31:35 AM EDT

Originally Posted By wengv:
reliability = quality ammo + quality gun.

Yes, piston guns take more tolerance to different ammo. If you use quality ammo, I don't see any big issue for gas guns.

The major drawback of m16/m4/ar15 is on its magazine design rather than its action.

Remember the benefits of the gas guns - light weight, light recoil, and less moving parts as you shoot. That is why people alway appreciate the accuracy of AR15.

I like gas guns and like piston guns too. They are different breed. They perform good result if you know how to operate them.



I 100% agree with you. But when you need your rifle to run no matter what , A piston wins out everytime.
And now we have the accuracy, ergonomics, and precision build of an AR with the reliability of an AK. What more can you ask for???
Link Posted: 2/25/2006 6:56:01 AM EDT
while the piston has its merits, it simply a waste of time and energy developing one for an AR based system,

the AR has preformed greatly in numerous conflicts, and is not as susptable as many would think, if a innovation was trulty needed, they israilies would of made a hybrid like there gallil out of the AR.

if you want to drop 1000-3000 dollars on an upper, be my guest, IMO the money would be better suited buying a real piston based gun like the SCAR or a converted Sig 556 to 552, you could even SBR any of those weapons and still be around the cost of a new colt upper, and well under the HK, if you can sell your soul to get HK to sell you one

Link Posted: 2/25/2006 6:57:49 AM EDT
REILABILITY can be improved with a gas piston system when using a can......
Link Posted: 2/25/2006 7:07:09 AM EDT
Maybe in the 1950's when the AR was being designed the technology was not there to have the lightweight, precision accuracy , and simplicity of the m16 while using a piston.

With todays technology lighter and stronger metals can be used without adding to much weight the AR15. This lets us have the advantage of a Piston op system without much sacrafice.

For us internet civilian warriors a direct gas AR is fine. But for a soldier, contract shooter, or law enforcement person a piston to me would be a high priority on my AR.
Link Posted: 2/25/2006 7:15:54 AM EDT
[Last Edit: 2/25/2006 7:19:00 AM EDT by chris157c]

Originally Posted By SRTM4:
The direct gas system works. There is no doubt about that. It is just alot more sensitive to different ammos, My AR has been fed more types of ammo than I care to think about, and has been 100% reliable, how is that sensitive?it blows dirty fouling gas right into your bolt carrier, which in turn gets your chamber filthy. I've ran thousands of rounds through an AR without cleaning anything other than the bolt face and barrel, with no malfunctions, so the filth means nothing. The direct gas impingement also heats the bolt carrier group very hot with all of those gases. This weakens extractor springs,ejector springs and eventually will weaken all of the metal components over time. Heat is an enemy to mechanical parts. But how much do all of the parts effected cost compared to the piston itself? in order for the piston to prove its worth it would need to be cheaper. replacing worn overheated parts on my current gas system not only eliminates both these problems where as the piston only addressed the heat, but it's cheaper than the piston. Not like wear or heat has been a problem for any of my AR's in the first place.
This is why I beleive in the gas piston. It solves these issues. It keeps the upper reciever parts including the bolt carrier group and chamber much cooler and cleaner.

Pistons are far less sensitive to weaker ammos, different buffer weights and buffer spring tensions. Through my testing ( very unscientific) that when fine tuning my direct gas AR's with different buffers and springs, it can make or break them. Don't play with something that isn't brokenDifferent barrel lengths, when matched up to the wrong buffer weights, using different ammos can ruin a direct gas gun. I've only seen this problem with SBR's, and I've never seen it ruin a gun, only make it malfunction, and it can be corrected cheaply, and once fixed will not be a problem again. the piston still costs too much.

My piston AR shoots any ammo, with any weight buffer or spring all of the time. It does this without even getting the bolt carrier group dirty or hot. Why would you need to change you buffer? Use the one that came with it and you will be fine in either system.
The piston does add some weight and more components to the mix, but to me it is well worth it. Especially for a foot soldier who needs his weapon to run.

The added weight, the added cost, no real benefit other than ease of cleaning, and a soldier is not supposed to modify the internals of his weapon, and should never have the need to anyway... I still can't bite on it...sorry
Link Posted: 2/25/2006 7:22:22 AM EDT

Originally Posted By chris157c:

Originally Posted By SRTM4:
The direct gas system works. There is no doubt about that. It is just alot more sensitive to different ammos, My AR has been fed more types of ammo than I care to think about, and has been 100% reliable, how is that sensitive?it blows dirty fouling gas right into your bolt carrier, which in turn gets your chamber filthy. I've ran thousands of rounds through an AR without cleaning anything other than the bolt face and barrel, with no malfunctions, so the filth means nothing. The direct gas impingement also heats the bolt carrier group very hot with all of those gases. This weakens extractor springs,ejector springs and eventually will weaken all of the metal components over time. Heat is an enemy to mechanical parts. But how much do all of the parts effected cost compared to the piston itself? in order for the piston to prove its worth it would need to be cheaper. replacing worn overheated parts on my current gas system not only eliminates both these problems where as the piston only addressed the heat, but it's cheaper than the piston. Not like wear or heat has been a problem for any of my AR's in the first place.
This is why I beleive in the gas piston. It solves these issues. It keeps the upper reciever parts including the bolt carrier group and chamber much cooler and cleaner.

Pistons are far less sensitive to weaker ammos, different buffer weights and buffer spring tensions. Through my testing ( very unscientific) that when fine tuning my direct gas AR's with different buffers and springs, it can make or break them. Don't play with something that isn't brokenDifferent barrel lengths, when matched up to the wrong buffer weights, using different ammos can ruin a direct gas gun. I've only seen this problem with SBR's, and I've never seen it ruin a gun, only make it malfunction, and it can be corrected cheaply, and once fixed will not be a problem again. the piston still costs too much.

My piston AR shoots any ammo, with any weight buffer or spring all of the time. It does this without even getting the bolt carrier group dirty or hot. Why would you need to change you buffer? Use the one that came with it and you will be fine in either system.
The piston does add some weight and more components to the mix, but to me it is well worth it. Especially for a foot soldier who needs his weapon to run.

The added weight, the added cost, no real benefit other than ease of cleaning, and a soldier is not supposed to modify the internals of his weapon, and should never have the need to anyway... I still can't bite on it...



Sounds like you are afraid to spend a little extra money for something better. Being a tightwad should not justify making your ar more reliable. For civilians thats Ok but for people who need to most reliable weapon available money would not be my biggest concern.

Tell all of your answers to the big manufactures that are starting to go piston op.
Link Posted: 2/25/2006 7:37:59 AM EDT
So, are you saying a Galil, FAL or M14 are better? It seems like they would be a much better way to go for the money and function.
Link Posted: 2/25/2006 7:43:57 AM EDT

Originally Posted By GroundFire201:
So, are you saying a Galil, FAL or M14 are better? It seems like they would be a much better way to go for the money and function.


No not at all.
I have been saying all along that the piston op is an added addition to the AR. The AR is very ergonomic, light, accurate and has the best of all worlds with a piston added to it.

Remember, dont knock a piston AR until you have fired one yourself.
I bought my POF M4 with a lot of doubt. After shooting it and comparing it to all of my other AR rifles Im sold and am now on the list to get another one.
Link Posted: 2/25/2006 8:16:29 AM EDT

...And now we have the accuracy, ergonomics, and precision build of an AR with the reliability of an AK.
What more can you ask for???



An AK chambered in 5.56mm.

I just had to have some fun there.

I like the new gas piston design; I like my AR design too. But my wallet just will not allow me to spend that kind of money. I take BigBore's advice: "spend the money on practice ammo". If I could afford one, I'd probably get it just to have.
Link Posted: 2/25/2006 8:17:44 AM EDT
[Last Edit: 2/25/2006 9:36:39 AM EDT by jaymeister99]

Originally Posted By SRTM4:
Maybe in the 1950's when the AR was being designed the technology was not there to have the lightweight, precision accuracy , and simplicity of the m16 while using a piston.

With todays technology lighter and stronger metals can be used without adding to much weight the AR15. This lets us have the advantage of a Piston op system without much sacrafice.

For us internet civilian warriors a direct gas AR is fine. But for a soldier, contract shooter, or law enforcement person a piston to me would be a high priority on my AR.



Actually the piston system dates back much further than the direct gas system, I remember reading about some type of gun going back to the late 1800s, but just before the M16 were the Garand, and the M14, both similar to the short stroke gas system. Eugene Stoner had developed a piston gas system that he did not use on the AR-10 (forerunner of the AR-15/M16). When the AR-15 was designed it was with the intent to have the lightest weight possible, and the simple gas tube was considerably lighter than the gas piston system.

The AR-15 was sold to Colt, and when the trials for a replacement to the M14 began it was entered. Armalite then had developed the AR-18, another Stoner design that was entered. It had a short stroke gas system, but word is it was quite heavier than the AR-15/M16.

Now fast forward 50 years later and this "new" gas system emerges again. But this time around there seems to be more of a push for reliability, accuracy, and overall a better gun rather than weight saving priority. Take a look at the M16A2, heavy barrel, handguards, another 2 pounds over the M16A1 I believe.

The direct gas system is not bad, bit theres something better now. Not just that but there are also better composite materials, stainless barrels, free-float handguards, lots of improvements that can be made. But IMO I always say if it isnt broke dont fix it.

The AR/M16 rifle works great as it is. But politics always play a part, and I doubt this will be any different. Most people with half a brain here will say make a new upper with free floats, stainless quick change barrel, new sights, and a piston system. That would work well, but I expect a huge push by uncle sam to ---- it up.
Link Posted: 2/25/2006 8:17:58 AM EDT
don't get me wrong SRTM4, I'm not saying your wasting your money, because all in all, it's what YOU want for your rifle. I personally don't see the need to spend money on an upgrade to a non problematic system, much like i think magpul followers are a waste because the standard green followers have never given me a problem. If it makes you sleep better at night, then who cares what I think. I just want the original poster to know that the standard system will never give him a problem, and that money can be better spend elsewhere.

Just trying to show all views, that's all...
Link Posted: 2/25/2006 8:26:55 AM EDT
Link Posted: 2/25/2006 8:31:45 AM EDT

Originally Posted By chris157c:
don't get me wrong SRTM4, I'm not saying your wasting your money, because all in all, it's what YOU want for your rifle. I personally don't see the need to spend money on an upgrade to a non problematic system, much like i think magpul followers are a waste because the standard green followers have never given me a problem. If it makes you sleep better at night, then who cares what I think. I just want the original poster to know that the standard system will never give him a problem, and that money can be better spend elsewhere.

Just trying to show all views, that's all...



I hear you Chris. I may get a little hot headed over this issue. You are right. Spend your money on where you see fit.

I just know now that Piston op AR's are that good and I hate to see people putting it down without trying it out for themselves.

Oh and I do also agree that more practice ammo would probably be the "Best Money Well Spent".
Link Posted: 2/25/2006 8:32:29 AM EDT
The piston system is advertised as more reliable because it is a cleaner running system

we all know what a dirty AR looks/operates like.
Link Posted: 2/25/2006 8:47:55 AM EDT
I'll wait for them to come down in price before jumping on the bandwagon
Link Posted: 2/25/2006 9:27:33 AM EDT

Originally Posted By redfisher:
The piston system is advertised as more reliable because it is a cleaner running system

we all know what a dirty AR looks/operates like.



This is part of my original question... If it's cleaner, where does the excess gas go? It doesn't enter the chamber/receiver, but it does still go up throught the gas port in the barrel. Where does it finally come out and take a dump?
Link Posted: 2/25/2006 10:05:53 AM EDT

I like to stick w/ what is widely used as standard issue.

Link Posted: 2/25/2006 10:33:02 AM EDT
I have a piston driven rifle..its called an M14..and me too Ill start using whatever is in use when the issued weapons change ..until then its DI for me
Link Posted: 2/25/2006 10:49:38 AM EDT
The direct gas system was designed to be an improvement over a piston based system... if it works, great, but it is really unnecessary. The AR15 in its original design is an excellent weapon. The piston upper is a marketing gimic.
Link Posted: 2/25/2006 11:00:30 AM EDT
I agree with the pro-DI comments. There are a lot of people saying that the AR-15 DI system "craps where it eats". Well, I've noticed that after shooting, the bolt face doesn't get as carboned up as many people think. The stoner DI system basically uses the 3 gas rings and the bolt as a "piston" (automotive engine style rings), whatever remaining gas residue MAY be deposited on the bolt face. The gas residue does not crap out onto the bolt face directly. That is why you see carbon buildup on the rear of the bolt.

Someone keeps posting their AR-15 that was never cleaned after 10,000 rounds of Wolf. I hope he keeps posting that because it's an awesome photo.
Link Posted: 2/25/2006 11:20:37 AM EDT
I'll take a crack at it.

First off all lets keep in mind that the DI system has its piston too, it is the rear of the bolt engaging in the hollow of the carrier forming the piston/cylinder.

Piston Pros:
less heat on bolt group and said lubricants

way, way, way easier to clean compared to thoroughly cleaning a DI gun

keeps critical operating parts cleaner during extraction, ejection, feeding, going in and out of battery

isn't as reliability sensitive to changes in barrel legnth, projectile weight, powder type/quality, chamber pressures etc

doesn't coat the internal working parts of the bolt/carrier group w/ sticky gunk that attracks fine sand and similar particles.

Piston Cons:
more moving parts to break

more (even if only a little) weight



Since I am so anal about cleaning weapons since I may not get them back out for a while, I really, really hate cleaning my ARs so being able to clean just the bore, bolt face and lugs, and gas piston would be really sweet. But, to do only the cleaning that is required to make the gun work well in a DI gun really isn't that hard, at least in low sand environments.

It sounds like a good point that the DI system was originally a weight saving/simplicity improvement over the piston systems of the 50's but no w/ better light weight piston systems, the benifits of the DI system are reduced.

One final and rarely mentioned note is that since the DI system puts positive pressure between the bolt and the carrier. Thus, it actually unloads the contact point at the bolt and barrel extension lugs during unlocking by pushing the bolt face against the base of the casing. W piston sysem, the carrier group moving rearward cams the bolt w/o dong anything to reduce the load on the afforementioned contact points. What this seems to say to me is that the DI system may do more enable tighter headspacing w/ reliability (barring other reliability issues) and reduce friction wear on locking lugs.
Link Posted: 2/25/2006 12:24:05 PM EDT
I have a regular upper on my civvy AR, but damned if anything that reduces the hours, and hours, and hours spent trying to get an M16 back to showroom condition wouldn't be an improvement.

A 15 minute cleaning job will get an M16 functional, but "functional" isn't the standard in garrison, "pristine" is.

In theory this would be easier with a piston upper.

That said, I've ran 600 rnds through my A2 during a CLFX in about 20 minutes (probably less) and it ran just fine. Other people's didn't, but mine did. I ended up burning up all the ammo for the soldiers who's weapons went belly up, and was tickled that my anal retentiveness about weapon maintainance paid off in rounds downrange.

Your sandbox results may vary.
Link Posted: 2/25/2006 12:28:04 PM EDT
[Last Edit: 2/25/2006 12:30:56 PM EDT by jaymeister99]

Originally Posted By metroplex:
I agree with the pro-DI comments. There are a lot of people saying that the AR-15 DI system "craps where it eats". Well, I've noticed that after shooting, the bolt face doesn't get as carboned up as many people think. The stoner DI system basically uses the 3 gas rings and the bolt as a "piston" (automotive engine style rings), whatever remaining gas residue MAY be deposited on the bolt face. The gas residue does not crap out onto the bolt face directly. That is why you see carbon buildup on the rear of the bolt.

Someone keeps posting their AR-15 that was never cleaned after 10,000 rounds of Wolf. I hope he keeps posting that because it's an awesome photo.



When the new M16A2 was adopted (late 80s) I remember an article in either Guns&Ammo or American Rifleman about the reliability of the new weapon and its improvements. What stood out more than anything was their reliability testing. They shot out 2,000 rounds NON-STOP without one jam, misfire, or any kind of problems. Not to mention this was with the older USGI mags before the green followers.

If it can stand up to that kind of abuse why bother changing it? If the rifle proves to be inferior in the desert environment then lets talk about a new system.
Link Posted: 2/25/2006 12:28:45 PM EDT

Originally Posted By rightwingnut:
Piston Pros: isn't as reliability sensitive to changes in barrel legnth, projectile weight, powder type/quality, chamber pressures etc


MAJOR conceptual error here.

A piston system is JUST as sensitive as a DI system to all the changes that you just mentioned. A piston system is designed to work around a given range of gas volumes and pressures. That range of pressures and gas volumes are controlled by the distance of the gas port from the chamber, by the pressure curve of the ammunition (i.e. the powder's burning rate), and by the max pressure created by the burning powder charge (chamber pressure).

I could go on to list the thermodynamic and mechanical equations at work here, but I don't think that is necessary. Suffice it to say that mechanically (in the mechanical engineering context) and thermodynamically, a DI system IS a piston system. The only difference is that it is missing the connecting rod or tappet because it is internal to the bolt.
Link Posted: 2/25/2006 12:39:27 PM EDT
[Last Edit: 2/25/2006 12:40:25 PM EDT by chris157c]

Originally Posted By halloween78:
I have a regular upper on my civvy AR, but damned if anything that reduces the hours, and hours, and hours spent trying to get an M16 back to showroom condition wouldn't be an improvement.

A 15 minute cleaning job will get an M16 functional, but "functional" isn't the standard in garrison, "pristine" is.

In theory this would be easier with a piston upper.

That said, I've ran 600 rnds through my A2 during a CLFX in about 20 minutes (probably less) and it ran just fine. Other people's didn't, but mine did. I ended up burning up all the ammo for the soldiers who's weapons went belly up, and was tickled that my anal retentiveness about weapon maintainance paid off in rounds downrange.

Your sandbox results may vary.



Call me old school, but cleaning your weapon is like shining your boots, and ironing your uniform. I did all, now the USMC has these suede boots, and noone has to spit shine anymore, and the uniforms have permanent creases, so noone has to iron anymore. while it saves on time, it makes it harder for me to know a squared away Marine from a shitbag. They make you clean the rifle like you shine your boots, and iron your uniform, attention to detail, so an inspector can see who's working hard, and whos slacking off. Shows me the leaders and the followers, and the proficiency and conduct will reflect such.

in combat you don't have to clean it inspection ready, you clean it to make it function properly. It's been done this way for 40 years (m16 era). All a piston is going to do is make the shitbags blend with the squared away.

Of course that's getting into the topic a little too heavy for most of the guys around here...
Link Posted: 2/25/2006 12:47:26 PM EDT
If piston uppers are made standard issue in 2006, we can expect to see threads like these within 1-2 years:
"How do I clean my piston?"
"How do I get rid of the carbon caked on the piston dish?"
"My piston feels loose, is this normal?"
"What is the best lube to use for the piston?"
"How do I clean the gas block?"
"Help, my piston upper AR is short stroking"

I have not handled a short stroke piston system before, but the AK piston system is VERY lenient. All it requires is a fairly tight seal at the gas block. After that, the gas "tube" is nothing more than an alignment system for the piston. I have 8 large holes drilled in there and it still throws steel cases 6-8 range stalls over to the right. It has managed to scratch and dent my BSA scope on the AR which was to the right of the Vepr. Unfortunately, you gain a lot of weight and lose some accuracy with that type of gas system. IMHO, you can't really beat the reliability of a blow back system. This may not be possible with rifle cartridges though, but it sure as heck works fine on pistol caliber SMGs and pistols.
Link Posted: 2/25/2006 1:19:05 PM EDT

Originally Posted By metroplex:
If piston uppers are made standard issue in 2006, we can expect to see threads like these within 1-2 years:
"How do I clean my piston?"
"How do I get rid of the carbon caked on the piston dish?"
"My piston feels loose, is this normal?"
"What is the best lube to use for the piston?"
"How do I clean the gas block?"
"Help, my piston upper AR is short stroking"

I have not handled a short stroke piston system before, but the AK piston system is VERY lenient. All it requires is a fairly tight seal at the gas block. After that, the gas "tube" is nothing more than an alignment system for the piston. I have 8 large holes drilled in there and it still throws steel cases 6-8 range stalls over to the right. It has managed to scratch and dent my BSA scope on the AR which was to the right of the Vepr. Unfortunately, you gain a lot of weight and lose some accuracy with that type of gas system. IMHO, you can't really beat the reliability of a blow back system. This may not be possible with rifle cartridges though, but it sure as heck works fine on pistol caliber SMGs and pistols.



+1 more problems than it's worth.

And it's not worth much. My AR w/o gas piston has run 100% even after 3000 rounds of Wolf.

All I know is that I don't need it. If you dont have confidence in the AR's gas system, by all means "upgrade".
Link Posted: 2/25/2006 1:45:43 PM EDT
I'm still trying to find that pic of the AR that was uncleaned after 10k+ rounds of Wolf. It has the standard gas tube/DI system
Link Posted: 2/25/2006 1:51:53 PM EDT

Originally Posted By rifleman2000:
The direct gas system was designed to be an improvement over a piston based system... if it works, great, but it is really unnecessary. The AR15 in its original design is an excellent weapon. The piston upper is a marketing gimic.



It's a gimmick until you run through a couple of thousand rounds in a carbine class and it comes time to clean.

A piston keeps fouling, carbon and heat out of the action and core of the AR15. How this is not seen as being an improvement and a good thing by some people astounds me
Link Posted: 2/25/2006 1:52:22 PM EDT
The bottom line.
Get a piston op AR and a direct gas AR. Run them until one stops. You will see th winner.
People can argue that direct gas AR's are great. In fact we all know that the AR is an awesome weapon. But History has said it a 1000 times that the direct gas has given reliability issues to the AR15. No doubt! That is a fact. Why cant a piston op system be better. The AK47 is the most reliable assault rilfle in the world. Noone argues that. What is so wrong with having an AR15 with all of its ergonomics, accuracy, smoothness etc and make it reliable like an Ak??????? People are so scared of change??? Why I do not know other than the tightwad syndrome. If a piston is more reliable( in which it is) why not go with it?

The US military is moving towards it. Specops want it Get over it people. It will be the future!!!
Link Posted: 2/25/2006 1:57:13 PM EDT
Link Posted: 2/25/2006 2:01:13 PM EDT
[Last Edit: 2/25/2006 2:02:58 PM EDT by metroplex]

Originally Posted By SRTM4:
The bottom line.
Get a piston op AR and a direct gas AR. Run them until one stops. You will see th winner.
People can argue that direct gas AR's are great. In fact we all know that the AR is an awesome weapon. But History has said it a 1000 times that the direct gas has given reliability issues to the AR15. No doubt! That is a fact. Why cant a piston op system be better. The AK47 is the most reliable assault rilfle in the world. Noone argues that. What is so wrong with having an AR15 with all of its ergonomics, accuracy, smoothness etc and make it reliable like an Ak??????? People are so scared of change??? Why I do not know other than the tightwad syndrome. If a piston is more reliable( in which it is) why not go with it?

The US military is moving towards it. Specops want it Get over it people. It will be the future!!!



Or rather the past.
The piston upper ARs are going to be overpriced initially, so I'll stick with my $7 gas tube, thank you very much.
Link Posted: 2/25/2006 2:01:56 PM EDT

Originally Posted By SRTM4:

The AK47 is the most reliable assault rilfle in the world. Noone argues that. What is so wrong with having an AR15 with all of its ergonomics, accuracy, smoothness etc and make it reliable like an Ak???????



Unless you loosen the clearances between bolt carrier and receiver, and bolt lugs and barrel extension, you will not achieve AK 47 reliability.
Link Posted: 2/25/2006 2:05:39 PM EDT

Originally Posted By SWO_daddy:

Originally Posted By SRTM4:

The AK47 is the most reliable assault rilfle in the world. Noone argues that. What is so wrong with having an AR15 with all of its ergonomics, accuracy, smoothness etc and make it reliable like an Ak???????



Unless you loosen the clearances between bolt carrier and receiver, and bolt lugs and barrel extension, you will not achieve AK 47 reliability.



Also, the gas piston on the piston upper ARs is not the same exact setup. On the AK, all of the crap gets blown right into the action and trigger group. Anyone that says otherwise has not shot and cleaned an AK. If I use too much CLP, my Vepr will blow a lot of that stuff back towards the shooter's face but its kept under the receiver cover. Sometimes it gets out! Hey, I've gotten hit DIRECTLY by a spent case when firing the Vepr, it just flew right out and nailed me in the head. I drilled vent holes (the Chinese Aks have vents as well as the Bulgarians) in my gas tube so a lot of the carbon and residue gets blown out. It reduces the amount of carbon built up on the piston, and reduces crap in the action/FCG area. My AR-15, OTOH, keeps the FCG relatively clean from powder residue and brass shavings.
Link Posted: 2/25/2006 2:06:54 PM EDT
[Last Edit: 2/25/2006 2:13:08 PM EDT by metroplex]
This is essentially the AK gas system (SVDs have shorter pistons):



On the AK the gas tube is "fluted" which allows excess gas to go PAST the piston and into the action. When firing dirty Wolf ammo through my Vepr, I will find red primer sealant, powder residue, and carbon everywhere inside the rifle and the magazines. It will also get all over the bolt face.

I know the HKs (including the 416) with short stroke pistons use a different design that prevents any of the residue from going back into the action, however I have been unsuccessful in finding any diagrams or photos of the system. I'm sure its reliable, but its either too expensive or unavailable, which puts it into the "I don't care" category for me.
Link Posted: 2/25/2006 3:11:28 PM EDT

Originally Posted By SWO_daddy:

Originally Posted By SRTM4:

The AK47 is the most reliable assault rilfle in the world. Noone argues that. What is so wrong with having an AR15 with all of its ergonomics, accuracy, smoothness etc and make it reliable like an Ak???????



Unless you loosen the clearances between bolt carrier and receiver, and bolt lugs and barrel extension, you will not achieve AK 47 reliability.



The AK uses a long stroke system, any type of piston system that may wind up on an AR will be a short stroke system. This is comparing apples to oranges.

The AK is a completely different type of weapon. Its designed almost solely to be reliable. Extremely loose tolerances. Besides being an assualt rifle it holds nothing in common with an AR. You can tinker all you want with an AR, its never going to have the same reliability as an AK in my book.
Link Posted: 2/25/2006 3:14:29 PM EDT

Originally Posted By jaymeister99:
The AK uses a long stroke system, any type of piston system that may wind up on an AR will be a short stroke system. This is comparing apples to oranges.


The length of the piston's stoke matters fuck all to reliability. If you think so, explain it in terms that a mechanical engineer (me) can understand, not "I read it on the internet".

Link Posted: 2/25/2006 3:16:42 PM EDT

Originally Posted By chris157c:
I think of it this way. How long has the U.S. Military been using the M16? If the piston stuff was all it is cracked up to be, why is it just now comming out ina big way? You can't tell me technology is changing, because gas piston systems have been out forever...

I feel it's just another guy trying to mak a buck with a new idea. Some fish will bite, others won't. It's just not the right lure to catch me...



The U.S. military isn't necessarily the same barometer that should be used in the consumer (civilian) market. There are lots of improvements in firearms design and accessory design that are offered to consumers but have not made their way into the U.S. miltary for whatever reason.

Consumers are being given a choice. The .mil is the .mil.
Link Posted: 2/25/2006 3:39:52 PM EDT

Originally Posted By SWO_daddy:

Originally Posted By rightwingnut:
Piston Pros: isn't as reliability sensitive to changes in barrel legnth, projectile weight, powder type/quality, chamber pressures etc


MAJOR conceptual error here.

A piston system is JUST as sensitive as a DI system to all the changes that you just mentioned. A piston system is designed to work around a given range of gas volumes and pressures. That range of pressures and gas volumes are controlled by the distance of the gas port from the chamber, by the pressure curve of the ammunition (i.e. the powder's burning rate), and by the max pressure created by the burning powder charge (chamber pressure).

I could go on to list the thermodynamic and mechanical equations at work here, but I don't think that is necessary. Suffice it to say that mechanically (in the mechanical engineering context) and thermodynamically, a DI system IS a piston system. The only difference is that it is missing the connecting rod or tappet because it is internal to the bolt.



I guess you are probably right. I was thinking about how w/ an external short stroke piston excess gasses that are above what is necessary to cycle the gun just blow out the relief ports in the cylinder, but that in the internal piston (DI) the gasses are more prone to over stroke the action, but it is the same in either case. With either system, an extremely high pressure load will make the action cycle harder and w/ a low enough pressure load the action will short stroke. Afterall the DI system has releif ports drilled into the carrier for extra gas to vent out.

The main significant difference is that the w/ the external action piston the gasses are vented into the air (or the handguard), while w/ the internal to the action piston setup the gasses, heat, and pollution are vented all over the working parts of the action.

I guess the solution w/ either internal or external piston system is to have an adjustable gas port so that w/ low pressure loads the action won't short stroke, but with high pressure loads the action won't hit the gun to hard.
Link Posted: 2/25/2006 3:44:28 PM EDT

Originally Posted By halloween78:
I have a regular upper on my civvy AR, but damned if anything that reduces the hours, and hours, and hours spent trying to get an M16 back to showroom condition wouldn't be an improvement.

A 15 minute cleaning job will get an M16 functional, but "functional" isn't the standard in garrison, "pristine" is.

In theory this would be easier with a piston upper.

That said, I've ran 600 rnds through my A2 during a CLFX in about 20 minutes (probably less) and it ran just fine. Other people's didn't, but mine did. I ended up burning up all the ammo for the soldiers who's weapons went belly up, and was tickled that my anal retentiveness about weapon maintainance paid off in rounds downrange.

Your sandbox results may vary.



In normal environments the DI system is as easy to clean as a system w/ an external piston when you mean cleaning it to the point that it will work.

But in the sand box, it is more important to clean the internal action surfaces to prevent them from becoming sand magnets. In this respect the external piston system has a significant tactical advantage over an internal piston system.

In other circumstances, the advantage is just in how easy it is to get the weapon to pristine clean.
Link Posted: 2/25/2006 3:48:32 PM EDT

Originally Posted By metroplex:
If piston uppers are made standard issue in 2006, we can expect to see threads like these within 1-2 years:
"How do I clean my piston...

...IMHO, you can't really beat the reliability of a blow back system. This may not be possible with rifle cartridges though, but it sure as heck works fine on pistol caliber SMGs and pistols.



You could use blow back on a 308, but to have a spring tension that could be manually operated the action would have to weigh literally almost 50 pounds to stay locked during peak pressures long enough to not go kaboom, or the spring tension would have to be so high you could not really pull it back and it would short stroke and fail to feed and crack the receiver.

The closets thing to a blow back system for rifle caliber pressures is the roller locker system of the HK G3 type weapon. It works good, but those things are boat anchors. I think my dad's weighs 11lbs empty.
Link Posted: 2/25/2006 3:49:03 PM EDT

Originally Posted By SWO_daddy:

Originally Posted By SRTM4:

The AK47 is the most reliable assault rilfle in the world. Noone argues that. What is so wrong with having an AR15 with all of its ergonomics, accuracy, smoothness etc and make it reliable like an Ak???????



Unless you loosen the clearances between bolt carrier and receiver, and bolt lugs and barrel extension, you will not achieve AK 47 reliability.



true dat
Link Posted: 2/25/2006 3:54:21 PM EDT
I do once remember a serviceman's post on a past thread about this topic. He said that since the fouling acts as a sort of lubricant as it comeout the expansion chamber, you can keep your gun completely dry and free of lubricant (except maybe for a drop of oil on the gas rings only) so that it doesn't attract sand and then when you fire it, it will kind of self lubricate.

That is just what he said. But then think about all the trouble you have to go throuhg to gett it to that point again after you fire it.
Link Posted: 2/25/2006 3:58:50 PM EDT
[Last Edit: 2/25/2006 4:19:19 PM EDT by jaymeister99]

Originally Posted By SWO_daddy:

Originally Posted By jaymeister99:
The AK uses a long stroke system, any type of piston system that may wind up on an AR will be a short stroke system. This is comparing apples to oranges.


The length of the piston's stoke matters fuck all to reliability. If you think so, explain it in terms that a mechanical engineer (me) can understand, not "I read it on the internet".




If you are an engineer then you apparently dont know "fuck all" about guns.

The long stroke system does not necessarily refer to the length of the piston's stroke. It refers to a single long one piece piston design like in the AK-47 which is directly impacted by the gas.

The short stroke design is a two or three piece design where a rod impacts another (the piston) which then runs to the bolt and/or bolt carrier (as opposed to the long stroke system where the piston is attached to the bolt carrier like on an AK-47 or the FN FNC and directly impacted by the gas). Does this explain it in terms that a mechanical engineer can understand, and not "I read it on the internet".

Short Stroke Systems:
AR-18
H&K G36
H&K 416

Long stroke:
AK-47
Sig 550
FN FNC
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