AR accuracy and barrel length

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tommy240

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Jan 20, 2010
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#1
I shoot long range bolt guns at all ranges from 100-1000 yards. I know that a 26 inch barrel will give me better muzzle velocity and accuracy at longer ranges than a 16-24 model using same ammo.

My question is with the gas block being located where it is, does a longer barrel have the same affect on muzzle velocity and accuracy like with a bolt gun?

With rule changes in some of the matches I attend they are opening up to AR plat forms and I am looking to get a bull barrel upper to go on my Colt Ar 15.

Any information would be appreciated.
 
#2
Re: AR accuracy and barrel length

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: tommy240</div><div class="ubbcode-body">I know that a 26 inch barrel will give me better muzzle velocity and accuracy at longer ranges than a 16-24 model using same ammo.</div></div>

Be careful what you "know".

Barrel length and accuracy are not necessarily related to one another.

A shorter barrel can be and frequently is more accurate than a longer one. The reason for longer barrels is velocity (as you mentioned) and sight radius (for iron sighted rifles).

Yes, in AR's a longer barrel has the potential for more velocity, however it's going to be dependent upon the load. There are lots of variables you need to pin down.

If I was building a .223 AR15 to compete with in tactical matches it would be a 18-20".
 
#3
Re: AR accuracy and barrel length

If you really wanna shoot 1000 with an AR you should pick a caliber before picking a barrel, 6.8spc or 6.5 grendel is about the best you can do ballistically in the AR15 line.

Bump up to an AR-10/SR-25 size and chamber in like 260 remington or 6.5 creedmoor or even .308win and have a really nice cartridge.

changing length of your gas tube requires knowing a fair amount about the round your going to shoot and even the load, some do it and report good results, I wouldn't do it on your first long range AR...
 
#4
Re: AR accuracy and barrel length

6.8SPC would be a worse choice than .223 for long range competition. It was designed for short range energy.

6.5 Grendel would be a better choice, but you are still hampered by case capacity.

THAT is the reason my 1000 yard semiauto is a AR10. When I get around to building a second upper it will be in .243, .260 or 7mm-08.
 
#5
Re: AR accuracy and barrel length

Barrel length has little to do with accuracy, that is absolutely correct, esp. considering the available loads. The AR platform is evolving into an extremely accurate gas gun, able to compete with bolts (we build for F-Class). Look at the various 6mm chambers if you want a 1000 yard AR. I've done a couple wildcats, the most recent being a necked-down version based on the 6.8 SPC cartridge (not Ackley improved). I chambered his on Krieger 7.7 416 SS blank, we worked up a nice load, and this shooter's grouping exceptionally well at 800.
 
#6
Re: AR accuracy and barrel length

I use my LR-308 for the thousand yard line but have heard great things about the 6.5 plus more ammo is being made for the 6.5 everyday so it shouldn't be long before there are some solid factory ammo out there for those who don't reload. Good luck with whatever you choose.
 
#7
Re: AR accuracy and barrel length

Thanks for the information.

I am planning on staying with 223 and range will probably not exceed 600yards for this build. If all works out good plan on building either an AR-10 platform in a 260 Rem. or 6.5 Creedmoor.

My current bolt is Rem. 700 in 6.5 x 47. Changed it from a 308 am a recoil woos.
 
#8
Re: AR accuracy and barrel length

I have a 26inch AR-15 that I have shot to 1000 yards quite a bit in F-TR competition. If you are looking at shooting only to 600 yards, you can do very well with such a rifle. The 26 inch barrel will provide extra velocity and with the .223, you can use all the velocity you can get for the longer range.
 
#9
Re: AR accuracy and barrel length

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body">I have a 26inch AR-15 that I have shot to 1000 yards quite a bit in F-TR competition. If you are looking at shooting only to 600 yards, you can do very well with such a rifle. The 26 inch barrel will provide extra velocity and with the .223, you can use all the velocity you can get for the longer range. </div></div>
+1
A 20" AR will serve you well out to 600yards, but 26" is the most common AR length for match uppers in XTC, F-Class, & prone. 26" is really a "must have" to compete at 1K: world of difference between 600yds and 1K
 
#12
Re: AR accuracy and barrel length

Absolutely. Also buy lots of brass, because you will only get one load out them when trying to get the velocity needed for the long trip down range and still arrive at a velocity above Mach 1.

You will also need to get your rifle looked at often because of the beating it will be taking. That 20 inch barrel is really short.
 
#13
Re: AR accuracy and barrel length

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body">Absolutely. Also buy lots of brass, because you will only get one load out them when trying to get the velocity needed for the long trip down range and still arrive at a velocity above Mach 1.

You will also need to get your rifle looked at often because of the beating it will be taking. That 20 inch barrel is really short. </div></div>
lol, tru dat
 
#15
Re: AR accuracy and barrel length

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sig685</div><div class="ubbcode-body">Absolutely. Also buy lots of brass, because you will only get one load out them when trying to get the velocity needed for the long trip down range and still arrive at a velocity above Mach 1.

You will also need to get your rifle looked at often because of the beating it will be taking. That 20 inch barrel is really short.</div></div>

Well, I get about 2800 fps from a 24.5 grain load of Re-15 under an 80 grain Berger, stuffed in Winchester brass primed with WSR's. There have been no pressure signs to indicate a need to scrap brass, even after a third firing. So far, the load gets bullets to 1000 yards nose-on; and, with low ES/SD, holding elevation is not too difficult. Last outing I had a 374 and something from 2 twenty shot for record strings.

One thing for sure, 1000 yard Service Rifle provides an opportunity for the shooter with the most skill to emerge victorious, no matter whether the shooter comes to the firing point with an AR or an M1A. The game's emphasis is on the shooter, not the gun.
 
#16
Re: AR accuracy and barrel length

24.5gr RE-15 might be ok for a bolt gun, but that is over the max recommended for an AR-15: by 0.7gr for an 80SMK for example. In service rifle you have no choice on barrel length. But, if the OP has a choice of barrel lengths, are you suggesting he choose 20" instead of 26"? I would not see the point of use 20" if you could choose longer...and the point is it REALLY helps to use a longer barrel with this cartridge.
 
#17
Re: AR accuracy and barrel length

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Scooter-PIE</div><div class="ubbcode-body">24.5gr RE-15 might be ok for a bolt gun, but that is over the max recommended for an AR-15: by 0.7gr for an 80SMK for example. In service rifle you have no choice on barrel length. But, if the OP has a choice of barrel lengths, are you suggesting he choose 20" instead of 26"? I would not see the point of use 20" if you could choose longer...and the point is it REALLY helps to use a longer barrel with this cartridge.</div></div>

First, I'm not shooting an SMK, 24.5 grains of Re-15 with the 80 grain Berger is not a problem for my gun. Second, shooting at LR with a .223, no matter what the barrel length, is ridiculous. There are other caliber choices, most of which will get any shooter better results. I mention shooting the AR based Service Rifle at LR as if you're going to be ridiculous why not do it with something that provides benefits. Service Rifle competition at LR does indeed have benefits, in fact, shooter/target analysis with the AR at LR will quickly reveal executing the firing task and knowing how to shoot are not synonymous. Service Rifle at LR demands shooter perfection that's hard for any to muster. Some are challenged by it, while others have no interest in getting into something that they perceive will embarrass them.

BTW, a longer barrel will usually assure higher velocity, translating to accuracy at greater distance, but at some point the bullet is still gonna begin to tumble, and that's where accuracy ends. But, think about this, put things in perspective, even the 14.5 inch M4 can get bullets from M855 to over 600 meters nose-on, meaning that for most needs out there in shooting land a relatively long barrel length may be moot.
 
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