any suggestions on a ar-10 .308 barrel length

[Hammer_Man]

DPMS pattern receivers are the most common, and most are "high" pattern at that. Depending on budget, I'd recommend a ZEV matched receiver set. ZEV bought out Mega, so they are basically Mega, but with updated styling. I built two AR10s using Mega MATEN receivers, and they were top notch. Criterion makes an excellent barrel, and so does Black Hole Weaponry. Barrel length depends on what you want to do. Personally I'd go with a 16" gun, as they make for a good general use rifle, and are easier to lug around on foot.

[deanq]

I built a 16" and a 20".
For "me", the difference is the gas system. 16" is mid length and is ammo finicky and required an adjustable gas block to be 100% reliable with the "one" load I run in it.
20" is rifle length gas, standard gas block, and is NOT ammo finicky and will run 100% with a larger ammo selection (not all 308 ammo is equal).
Pick your poison. Each configuration has it's plus/minuses. Pick what's best for you/your mission. Best tool for the job and all that.....JMHO YMMV

[Hammer_Man]

I built a 16" and a 20".
For "me", the difference is the gas system. 16" is mid length and is ammo finicky and required an adjustable gas block to be 100% reliable with the "one" load I run in it.
20" is rifle length gas, standard gas block, and is NOT ammo finicky and will run 100% with a larger ammo selection (not all 308 ammo is equal).
Pick your poison. Each configuration has it's plus/minuses. Pick what's best for you/your mission. Best tool for the job and all that.....JMHO YMMV

If you don't mind, what brand manufacturer made your barrels?

[Leonardo]

16" or 20".
Anything in between is not worth the other negatives.
Ammo selection and barrel quality/profile will mean way more in performance than barrel length.

This.....^^^

[deanq]

If you don't mind, what brand manufacturer made your barrels?

Brownells brand. I don't know who Brownells has make them

[JediGuy]

Brownells are/were made by Faxon.

[Hammer_Man]

Thought I'd add my .02 cents. I custom ordered a 20" barrel from Blackhole Weaponry this weekend, because they're running a 30% off coupon through June 1st. It's a standard profile (heavy under the handguard, .750 from the gas block forward), rifle length gas system, with honey comb pattern fluting, and FDE cerakote. Regular price on this setup is $605, but with the coupon applied it's $448 shipped. Now I just have to wait 8-16 weeks for it to be produced, and sent out. I've used Blackhole barrels on other builds, and I find them to be pretty accurate, and very easy to clean. Initially I wanted to run a 16" - 18" barrel, but I wanted to punch out to 1k meters, so I figured a full sized 20" barrel would serve me better. We'll see how it all turns out.

[Grim.Patriot]

Tho I haven’t built a 7.62 NATO AR, I do own several 308 AR’s from a 12” Sig SBR to a 20” LWRC REPR-II. I have chrono’ed all of them and find a significant velocity increase with increased barrel length. For long range shooting, go with 20” barrel. For hunting, all depends on terrain your hunting in. If you need long range go with 20”, for a fast action shooter, the shorter 16” may be better option.

[NQNPIII]

Why do I see no love for the 18" here? I went the easy route and bought a PSA G2, and a G3 lower. Then grabbed a G3 18" stainless barreled upper. 6 different factory loads have ran 100% including Wolf. No idea what the gas block is set at. Right now it doesn't matter.

[Hammer_Man]

Why do I see no love for the 18" here? I went the easy route and bought a PSA G2, and a G3 lower. Then grabbed a G3 18" stainless barreled upper. 6 different factory loads have ran 100% including Wolf. No idea what the gas block is set at. Right now it doesn't matter.

I've used 18" barrels in the past, and they functioned just fine. The thing is, if you need a short barrel just get the 16". If you really care about projectile velocity than get a 20".