I did a search and I also looked at the ammo oracle and couldn't nail it down.

I have the option of buying either a 14.5" LE6921 with a perm Vortex or a 16.1" LE6920

What am I really losing in terms of muzzle velocity and ballistics, especially with the heavier rounds?

While we are all here, which one would you take?

Thanks,
Cameron

No option for neither?

Quoted: I did a search and I also looked at the ammo oracle and couldn't nail it down. I have the option of buying either a 14.5" LE6921 with a perm Vortex or a 16.1" LE6920 What am I really losing in terms of muzzle velocity and ballistics, especially with the heavier rounds? While we are all here, which one would you take? Thanks, Cameron

I asked a similar question not too long ago. It will make no noticible difference unless you start shooting out to 500 yds. For most shooting under 200 yds you wont see any real difference in bullet drop.

16" is as small as I would go.

Quoted: The 16" is the better choice, but the 14.5" looks cooler.

I agree.  The 14.5's do look a lot cooler, and I prefer a shorter length.  But most of us are not clearing buildings for a living.  The permanent attachment is a real pain, because it limits some of your options on barrel and forearm modifications.  The extra velocity from a 16", while not huge, is always a good thing.

I don't expect to be clearing rooms with my AR any time if at all so I firmly believe that more velocity is always better. I also believe that a non-permently attached flash suppressor is preferable to the inverse.

Quoted: 16" is as small as I would go.

+16

Does anyone know the actual or approx. feet/second I would lose with a 1.5" reduction in barrel length?

Thanks,
Cameron

The 1.5" difference in bbl length loses about 68 f.p.s. but that's not the whole story. Shooting XM193 (mil spec 55gr ammo), you will lose about 15 yds of fragmentation range with a 14.5" bbl. If you shoot something heavier, with a thinner jacket (e.g. 75gr or 77gr ammo), you will be able to extend the fragmentation range of the 14.5" to 110 yds (75gr) and 145 yds (77gr). With a 16" bbl, you will get fragmentation out to 150 yds (75 gr) and 170 yds (77gr).

Matt,

Thank you for taking the time.

I appreciate the information.

Cameron

From Bushmaster:

5 shot groups, 3 different bbls of same length:

14.5 in. 55gr. 3064fps,   1146 Ft/Lbs.
14.5 in. 62gr. 2907fps,   1163 Ft/Lbs.  
16 in.    55gr. 3132fps,   1198  Ft/Lbs.  
16 in.    62gr. 2989fps,   1230  Ft/Lbs.  
Mil spec ammo I believe.

Your not going to get a LE6921 like that as LE6921 are already SBRs!!!

Your going to need a LE6920 then do the barrel work.

Saying that----get the LE6920 and get a 14.5 with Perm FH upper and have both!!!

Read the ammo oracle and learn why longer is better!

Quoted: The 1.5" difference in bbl length loses about 68 f.p.s. but that's not the whole story. Shooting XM193 (mil spec 55gr ammo), you will lose about 15 yds of fragmentation range with a 14.5" bbl. If you shoot something heavier, with a thinner jacket (e.g. 75gr or 77gr ammo), you will be able to extend the fragmentation range of the 14.5" to 110 yds (75gr) and 145 yds (77gr). With a 16" bbl, you will get fragmentation out to 150 yds (75 gr) and 170 yds (77gr).

Im not getting the 75 and 77 grain figures... 75 grain is lighter thus higher velocity with the same charge plus has better BC so it slows less.  75 has the longer frag range, not by any amount to even consider but its not less as you have posted.  Where do these figures come from?

A 11.5" barrel will allow a 75 grain 5.56 TAP round to fragment just beyond 100 yards.  Another 3" does not add 5 or 6 yards to that.

Quoted: 75 grain is lighter thus higher velocity with the same charge plus has better BC so it slows less.

Why would a 75gr bullet have a better BC than a 77gr?  Is this a difference in bullet design?  I would imagine - if the bullets were identical, the 77 would have a better BC, no?

I'd personally buy the 16" so I could run a suppressor without having to double stamp the setup.  

Quoted: The 16" is the better choice, but the 14.5" looks cooler.

+1

Quoted: I'd personally buy the 16" so I could run a suppressor without having to double stamp the setup.

If I could afford the price and hassle of a NFA supressor... I'd already have an SBR... with all kinds of uppers.

Quoted: Im not getting the 75 and 77 grain figures... 75 grain is lighter thus higher velocity with the same charge plus has better BC so it slows less.  75 has the longer frag range, not by any amount to even consider but its not less as you have posted.  Where do these figures come from? A 11.5" barrel will allow a 75 grain 5.56 TAP round to fragment just beyond 100 yards.  Another 3" does not add 5 or 6 yards to that.

My numbers are from the .223/5.56 Fragmentation Charts post in the Ammunition forum. The numbers made sense to me because the 77gr has a thinner jacket. If the numbers are posted are out of date well then the charts are out of date. It's been over a year and half since the original post in that thread was updated.

Quoted: Read the ammo oracle and learn why longer is better!

I think the ammo oracle should include other facts like:

Average police shooting distance in the last 50 years.
Average civilian self defense shooting distance in the last 50 years.
Average police sniper shooting distance in the last 50 years.
Longest ever police shooting distance in the ast 50 years.
Longest ever civilian shootig distance in the last 50 years.

By covering all shootings ever in the US borders you would see that ther would be no real advantage to a barrel over 10.5 to 11.5" and certainly no need for a barrel over 14.5" if your sole consideration is self defense against humans and you are using the best available 5.56 ammunition.  I know Brouhaha uses all 16" barrels but I dont see a point in one unless its a dedicated long range (over 100 yards for civilian self defense) puposes.

Quoted: Quoted: Im not getting the 75 and 77 grain figures... 75 grain is lighter thus higher velocity with the same charge plus has better BC so it slows less.  75 has the longer frag range, not by any amount to even consider but its not less as you have posted.  Where do these figures come from? A 11.5" barrel will allow a 75 grain 5.56 TAP round to fragment just beyond 100 yards.  Another 3" does not add 5 or 6 yards to that. My numbers are from the .223/5.56 Fragmentation Charts post in the Ammunition forum. The numbers made sense to me because the 77gr has a thinner jacket. If the numbers are posted are out of date well then the charts are out of date. It's been over a year and half since the original post in that thread was updated.

That chart is comparing 75 grain .223 Balck Hills vs 5.56 pressure 77 grain MK262 seconds.  You forgot to note the pressure difference.  .223 77 grain would have less velocity at a give range than 75 grain if you used 77 grain .223 Black Hills.

Quoted: I'd personally buy the 16" so I could run a suppressor without having to double stamp the setup.

Its only another $200 and ints not double stamped like an MP5SD its two seperate stamps that have nothing to do with one another.  A 16" barrel and seperate suppressor is LONG and nose HEAVY.  I cant really see why youd run a 16" AR with suppressor unless its a precision rig.  Becomes very clumsy indoors and can easily be longer than a 20" barreled rifle with A2 flash suppressor.

Quoted: Quoted: Read the ammo oracle and learn why longer is better! I think the ammo oracle should include other facts like: Average police shooting distance in the last 50 years. Average civilian self defense shooting distance in the last 50 years. Average police sniper shooting distance in the last 50 years. Longest ever police shooting distance in the ast 50 years. Longest ever civilian shootig distance in the last 50 years. By covering all shootings ever in the US borders you would see that ther would be no real advantage to a barrel over 10.5 to 11.5" and certainly no need for a barrel over 14.5" if your sole consideration is self defense against humans and you are using the best available 5.56 ammunition.  I know Brouhaha uses all 16" barrels but I dont see a point in one unless its a dedicated long range (over 100 yards for civilian self defense) puposes.

But my guns aren't for civilian self defense, silly rabbit.

They are for the Revolution!  

Quoted: That chart is comparing 75 grain .223 Balck Hills vs 5.56 pressure 77 grain MK262 seconds.  You forgot to note the pressure difference.  .223 77 grain would have less velocity at a give range than 75 grain if you used 77 grain .223 Black Hills.

You are absolutely right. Thank you for catching that.

Quoted: Quoted: I'd personally buy the 16" so I could run a suppressor without having to double stamp the setup.   Its only another $200 and ints not double stamped like an MP5SD its two seperate stamps that have nothing to do with one another.  A 16" barrel and seperate suppressor is LONG and nose HEAVY.  I cant really see why youd run a 16" AR with suppressor unless its a precision rig.  Becomes very clumsy indoors and can easily be longer than a 20" barreled rifle with A2 flash suppressor.

I know the ins and outs of that pretty well.   If you run a 14.5 it's only 1.5" shorter with the can on the end, hardly a major difference and certainly not worth the extra $200 tax.    I will say that a 10" or less is worth the stamp.     I run one on a 16" barrel and although it's long it's not too unwieldy.   My integral at 16.5" total length is much better tho!

You can buy a suppressor for as little as $400+ tax.    It is worthwhile, DO IT

NFA Investments has suppressors locally you can buy for UNDER $400 plus tax.  Its not $200 for the 1.5" you are paying for... its the convenience of removable flash hiders and the future 10-11" uppers you will buy.

16" bbl 55grain loads 2700 ft/sec threshold range approx 100 yards.
M193 100yards 2720 ft/sec above threshold - 125yards at 2625 ft/sec below threshold

14.5" bbl 77grain loads 2300 ft/sec threshold range approx 125 yards.
MK262 125 yards 2345 ft/sec above threshold - 150 yards at 2286 ft/sec below threshold

So... effective fragmentation range is determined more by bullet weight (thinner jacket) (400fps) than by barrel length (50-100fps), and a we can see that the 14.5 has a greater effective range with the heavier round.

Take it a step further and at 500 yards the heavier round 77gr out of the shorter barrel 14.5" is actually traveling FASTER than the 55gr out of the 16" and hits with 160% more energy!

Conclusion: with a 77grain round a 14.5" 1 in 7 twist barrel has a greater effective range than a 16" 1 in 9 twist barrel with a 55grain?


I BTW the 14.5" w/ perm Vortex is NOT an NFA gun.

Quoted: Quoted: 75 grain is lighter thus higher velocity with the same charge plus has better BC so it slows less.   Why would a 75gr bullet have a better BC than a 77gr?  Is this a difference in bullet design?  I would imagine - if the bullets were identical, the 77 would have a better BC, no?

77 grain = Sierra (that's the company that makes it)
75 grain = Hornady (that's the company that makes it)

They have different designs.  Albeit they are similar if you're comparing every .224 bullet there is made, they are definitely very  similar.  But when you compare just the 2 they are very different.  And sierra's cost more.  I thought the Sierra's had a higher BC?

I got a box of bh blue 77's to try.  I'm afraid that my barrel might like them because I'll want to buy more than.  I was going to try the 75's but midway was all sold out.  Where do you guys get the 75's in smaller quantities than half a case??

Quoted: Quoted: Quoted: Read the ammo oracle and learn why longer is better! I think the ammo oracle should include other facts like: Average police shooting distance in the last 50 years. Average civilian self defense shooting distance in the last 50 years. Average police sniper shooting distance in the last 50 years. Longest ever police shooting distance in the ast 50 years. Longest ever civilian shootig distance in the last 50 years. By covering all shootings ever in the US borders you would see that ther would be no real advantage to a barrel over 10.5 to 11.5" and certainly no need for a barrel over 14.5" if your sole consideration is self defense against humans and you are using the best available 5.56 ammunition.  I know Brouhaha uses all 16" barrels but I dont see a point in one unless its a dedicated long range (over 100 yards for civilian self defense) puposes. But my guns aren't for civilian self defense, silly rabbit. They are for the Revolution!

Yeah, and even though some of you whine about it, some of us use it for deer hunting.  I bought a 16.  I had a 20 but it got handed down, for now,  to my brother when I got my 16 so we could all have one!!!

Devl makes a very valid point. IIRC the specifics, the longest "justifiable homocide" in the line of duty was a 97 yard shot taken by a SWAT sniper in TX. I believe the suspect was holding a young child hostage in a motor vehicle when the SWAT sniper neutralized the suspect with a shot to the head, ending the standoff. The majority of PD shootings are conducted using handguns, as this is the most prevalent weapon. Handgun distances are almost always less than 30 yards, at least in PD work. As a civilian, you are going to have a VERY hard time justifying a 30 yard shot, let alone a 100 yard shot. Unless your state has adopted the "castle law" your first responsibility when faced with the threat of death/serious injury is to flee, even if you are in your own home. If you are

unable to flee, and only if you cannot escape, can you respond with equal or lesser force. 30 yards between you and your target is generally enough distance to flee or take evasive measures. If you are buying an AR for strictly HD work, barrel length will have no bearing on the weapons effectivenss. As a civilian under generally normal circumstances*absent of martial law, anyways...* a 11.5/14.5 inch barrel will provide enough fragmentation range to defend life and limb. A 14.5 inch barrel with permanantly affixed FH will be slightly shorter which will make for a more compact weapon, which is an advantage in close quarters. I personally oppose the 14.5 inch

barrel length. Besides being shorter, it is actually determental to our troops who use it. A 16 inch barrel is plenty compact, especially with stock collapsed and increased range is more usefual than affixing a bayonet...unless Napoleon reforms his army and rides accross the plains of North America. 16 inches is probably the best compomise and the most universal choice. While its not as "authentic" its more functional, which should be more important....at least to non-airsoft types.

Quoted: Devl makes a very valid point. IIRC the specifics, the longest "justifiable homocide" in the line of duty was a 97 yard shot taken by a SWAT sniper in TX. I believe the suspect was holding a young child hostage in a motor vehicle when the SWAT sniper neutralized the suspect with a shot to the head, ending the standoff. The majority of PD shootings are conducted using handguns, as this is the most prevalent weapon. Handgun distances are almost always less than 30 yards, at least in PD work. As a civilian, you are going to have a VERY hard time justifying a 30 yard shot, let alone a 100 yard shot. Unless your state has adopted the "castle law" your first responsibility when faced with the threat of death/serious injury is to flee, even if you are in your own home. If you are unable to flee, and only if you cannot escape, can you respond with equal or lesser force. 30 yards between you and your target is generally enough distance to flee or take evasive measures. If you are buying an AR for strictly HD work, barrel length will have no bearing on the weapons effectivenss. As a civilian under generally normal circumstances*absent of martial law, anyways...* a 11.5/14.5 inch barrel will provide enough fragmentation range to defend life and limb. A 14.5 inch barrel with permanantly affixed FH will be slightly shorter which will make for a more compact weapon, which is an advantage in close quarters. I personally oppose the 14.5 inch barrel length. Besides being shorter, it is actually determental to our troops who use it. A 16 inch barrel is plenty compact, especially with stock collapsed and increased range is more usefual than affixing a bayonet...unless Napoleon reforms his army and rides accross the plains of North America. 16 inches is probably the best compomise and the most universal choice. While its not as "authentic" its more functional, which should be more important....at least to non-airsoft types.

Not in NY. I dont know about the other states but here if someone enters your home or any dwelling in which you could be sleeping IE a house, camper, RV, mobile home, apartment, etc. you can blow the crap out of em and get away with it. As long as you "feared for your life". No such thing as necessay or equal force in this case, you can unload 100 rounds on em and its 100% legal.

Out on the street, outside your dwelling you need to respond with equal force, but not inside your home.

You might get more velocity out of a 14.5 than a 16 inch (I know not the norm but it happens) I have a 14.5 Bushmaster thats faster than my 16 inch Bushmasters, had another that was close only 30 fps slower. Don't worry about it , buy what you like the looks of.
Smokem 1

Paper tangos can't tell the difference.

When comparing velocities and effective framentation ranges, there is something to consider that no one has brought up.

Because the 16" barrel has a higher MV than the 14.5", the range at which the bullet will fragment is approximately 15 yds greater than with the 14.5".  What does that mean in practical terms?  Up to the point where the bullet from the 14.5" will no longer fragment, performance is the same.  For 15 yds, the 16" barrel out performs the 14.5".  Beyond that distance they again perform essentially the same.

When you're talking a couple of inches in barrel length difference, you've only got a narrow range window in which performance differs.  Narrow window between 20" and 16".  Narrow window between 16" and 14.5".  Big window between 20" and 14.5".

So, with that in mind, review your priorities.  For many, appearance is a big factor.  The rifle is a paper plinker with only a remote possibility of actual use in a defensive situation.  If you do have to use it, legitimate civilian defense will probably mandate its use at pretty close range.  Consequently, long range terminal ballistics are not a huge concern.  The 14.5" will be handier than the 16", which for a civilian, defensive weapon is not a bad thing.  

In conclusion, get which one suits your fancy.  At worst, there will be a 15 yard window in which the longer barrel provides superior performance.  Otherwise, performance is equal.  The 16" is a good compromise between the long 20" and the short 14.5".  Only you can decide if that compromise is important to you.

If you are talking about hunting, then I would say definately go with as long a barrel as is comfortable to use in your terrain.

Quoted: When comparing velocities and effective framentation ranges, there is something to consider that no one has brought up. Because the 16" barrel has a higher MV than the 14.5", the range at which the bullet will fragment is approximately 15 yds greater than with the 14.5".  What does that mean in practical terms?  Up to the point where the bullet from the 14.5" will no longer fragment, performance is the same.  For 15 yds, the 16" barrel out performs the 14.5".  Beyond that distance they again perform essentially the same. When you're talking a couple of inches in barrel length difference, you've only got a narrow range window in which performance differs.  Narrow window between 20" and 16".  Narrow window between 16" and 14.5".  Big window between 20" and 14.5". So, with that in mind, review your priorities.  For many, appearance is a big factor.  The rifle is a paper plinker with only a remote possibility of actual use in a defensive situation.  If you do have to use it, legitimate civilian defense will probably mandate its use at pretty close range.  Consequently, long range terminal ballistics are not a huge concern.  The 14.5" will be handier than the 16", which for a civilian, defensive weapon is not a bad thing.   In conclusion, get which one suits your fancy.  At worst, there will be a 15 yard window in which the longer barrel provides superior performance.  Otherwise, performance is equal.  The 16" is a good compromise between the long 20" and the short 14.5".  Only you can decide if that compromise is important to you. If you are talking about hunting, then I would say definately go with as long a barrel as is comfortable to use in your terrain.

I like your post.  I'm tired of people being called airsofters just because they want the looks of what the military uses.  For crying out loud, it's an AR forum.  The AR is the civilian equivalant of an M16 / M4.  So I should buy a 16" just because I'm not trying to copy the military?  Give it up.    It's a military arm, in whatever configuration you got it's closer than anything else.  I almost chose the 14.5 with the M4 profile because #1 it does look like a military arm, and #2 it may be a slight handier inside.  But I'm going to use mine for hunting and figured the 16" might be a little better.  Plus, I like ADCO's products and I bought what he offered.  But for crying out loud this airsoft talk is bullsh--.  When I got a garand and a carbine it was because my grandpa might have carried one in France and died doing so.  Why should it be so different now?

Just so you know dorsai, I was referring to what rhyno said.  I totally agree with all your reasoning which is why I quoted it.

I was wondering, will there be any noticable performance difference out to 300 yards in reguards to accuracy? Will a 55, 62, or 75 grain bullet hit much lower out of a 14.5'' barrel? I've been thinking about getting a lightwieght, compact, reliable, and simple rifle for multi-gun matches, and I'm wondering if a 14.5'' would do the trick, or if i should get a 16''.  

It is not just a matter of effective range of fragmentation. I doubt seriously that I would take a shot at someone at 100 yds range. Where is the need for self-defense, unless he is shooting at me with a rifle also?

So, let's not look at the maximum range of fragmentation charts. Look instead at the photos that show what kind of fragmentation you get at different speeds.

The faster the speed, the greater the fragmentation. The greater the fragmentation, the greater the wounding capacity. The greater the wound, the more likely that the encounter is successfully ended.

So, even though (for example) XM193 will fragment reliably from a 14.5 inch barrel at 40 yds, you are still going to get more fragmentation from a 16" barrel at the same range.

If that is important to you, then go with the 16". If you think the 14.5" performs adequately at these ranges, then get that one if you like it better.

It often comes down to subjective reasons, no matter how we try to objectify. For my 2nd AR, I got a 16" with a collapsible stock. I wanted a trunk gun, so compactness was important. But since  am outdoors a lot, and this is not just meant for a self-defense weapon, I did not want to give up that extra range, so I chose the 16". Someone else could have chosen differently for their own reasons, and they would not have been wrong.

Quoted: When comparing velocities and effective framentation ranges, there is something to consider that no one has brought up. When you're talking a couple of inches in barrel length difference, you've only got a narrow range window in which performance differs.  Narrow window between 20" and 16".  Narrow window between 16" and 14.5".  Big window between 20" and 14.5".

I really wonder about the difference in wound profile between a 20" and a 14.5" at 30 yards.  Most of the info we read on this indicates the difference is small because the primary wound mechanism is fragmentation, but the 20" would be carrying about 170 fps/130 ftlb more and surely this has a significant effect.  At least reports from Afghanistan and Iraq tend to support it's superiority even at short ranges.

To answer the question I would go with the 14.5"/Vortex or Phantom with standard handguards, the 16" in a mid-length with a rail.  BH 75gr OTM ammo will give satisfactory fragmentation performance in even a short 14.5", if it's of particular concern, get a 20" to give fragmentation out to 200 yards, it's a good backup to a 14.5".  
It's what I did, when somebody asks me about why I have a "long" 20", I spout all kinds of fragmentation statistics!  
If at another time someone asks me about the "short" 14.5", I let them have it with the fragmentation stuff again, just putting a different slant on it.

BOTH!


get the 16in midlength--great looks like the 14.5, same benefits as the 16 and then some...