View Full Version : AR Barrel Length

03-08-2013, 12:37 PM
This thread is intended to discuss the advantages and disadvantages of various barrel lengths on the AR platform.

03-08-2013, 12:39 PM
I understand that one of the primary considerations for barrel length is velocity and selection of length of gas system.

What is the disadvantage of an 18" barrel? You get a longer sight radius for iron sights, the option for a mid-length gas system, and higher velocity which means a flatter flight trajectory, right?

I'm not concerned about weight because I lift hard and am not planning any LRRP missions in the near future. Is 16" vs. 18" that big of a deal in close quarters?


03-08-2013, 1:55 PM
In close quarters, shorter is better. And lower mass/reduced inertia in the barrel tip is better to quickly swing the barrel to the POA. Thus for cqb, a 14.5 pencil with a lightweight welded on muzzle extension (tm) is likely best.
On the other end is a longer barrel for increased velocity, but not so long as to reduce accuracy due to vibrational harmonics. For .223, it's likely a max of around 20" or so. Any more and you get harmonics without much increased velocity, any less and you trade off velocity. This is for a constant (and presumably heavy/bull) barrel weight.
FWIW, I ordered a Stag 3G (L) and though a great rifle, it's a bit too much of a compromise. It's somewhat heavy to carry and to swing quickly, and perhaps a bit too short for the best mid-range accuracy though it's much better at the latter than the former.
My next one will be a pencil/short/light thingie with a CF fore-end, a metal-frame/fixed length stock (name escapes me), all designed to be lightweight. Much nicer to hold/carry/point.

03-08-2013, 3:38 PM
Ahhh...Ah-heeehm, I believe the primary driver here is the caliber - just sayin.

Is the question for the .223 or the .458 SOCOM?

03-08-2013, 4:40 PM
.223/ 5.56 NATO is what I'm looking at.

03-08-2013, 4:55 PM
According to Randall (our Calguns resident AR expert for SoCal) 18" with rifle length gas and a medium weight barrel, if running optics.

I shoot 3 gun and started with a rifle I picked up on consignment. It was 20", rifle length, and Bushmaster Hbar. Randall turned it down to 0.700" under the handguard and shortened it to 18", and re-threaded it for my 1.5 battle comp (they didn't have a 1.0 in stock). He said any less than 18 would be harsh or less reliable for the gas system and any less than .700" would allow the barrel to move too much with optics. FSB iron sights could use a thinner barrel due the the front sight moving with the barrel and therefore not effecting the accuracy as much.

My gun (with an A2 butt-stock and handguards) seemed very front heavy before. After Randall got the MI Gen 2 SS light weight hand guard on and reworked the barrel, it really made a big difference in handling. I shaved down the original FSB to fit under the 1.5"x15" hand guard.

I am new to 3 gun and AR's, but this gun shoots nice at 7lbs 6.8 oz. I am still working on my longer range shots, and am more of a pistol shooter than a rifle shooter. My AR is easy to use around barricades.

My brother has a Stag 3G, complete rifle, with 1.25x4 power scope. It is 2 pounds heavier, and is much harder to handle. It has a fluted stainless barrel.

I shot another AR with the same barrel treatment as mine, but the owner used a low mass bolt/and or carrier and low mass buffer. Randal suggested this mod to me. I now know that he was definitely right with that recommendation. My rifle has a slight kick (it makes double taps a little slower) but this rifle was like shooting a 10/22. The gun didn't move.

Randall is also a precision shooter, so he knows a thing or two about accuracy. I don't regret following his recommendations one bit. More experienced rifle shooters may have a more informed opinion than I can give you here.

03-08-2013, 4:59 PM
Fvck me, just had a major de ja vu moment as I edited my last post and had thoughts of what I just learned about .458 SOCOM.

Thanks for the posts. For now, I'm leaning towards a Daniel Defense as my first AR because who knows when a Sig or Smith will show up. I will probably go with a 16" or 18".