The suppressed 5.56 AR. What barrel length?

[flux]

I don't have to deal with tax stamps etc, so keep that in mind when answering .
My primary AR is a 14.5", but I'm contemplating getting something shorter to run a suppressor on most of the time, and possibly make it my go to rifle. 300blk would be great, but ammo is steeply priced here, even if i reload. So, for a 5.56 rifle, what barrel length makes the most sense in terms of terminal ballistics as well as size. We do have ASE suppressors available here.

[Default.mp3]

Some people will argue for a 10.3", to keep the OAL of the gun with the suppressor as short as possible. Others will argue for a 11.5", which is suppose to have noticeably better reliability (due to increased dwell time and all that), and has only 1" more than a 10.5", which is an arguably negligible difference in length for most applications; note that you can have an extremely reliable 10.3", so long as you properly tune to combination of gas ports, buffer, RE spring, bolt carrier, and ammo, the 11.5" simply gives you a wider window to work with.

[rob_s]

I am of the 10.3 sentiment, and wouldn't waste too much time monkeying with springs, buffers, etc. I'd get an adjustable gas block (infinitely adjustable, not the on/off type) and make sure the bolt locked back reliably with it cranked down as small as possible and be done.

When you say "terminal ballistics" you're going to have to provide more information about what you mean and what your personal requirements may be.

[Gadfly]

I run a personally owned 10.5" FN barrel I got from PSA. Runs like a champ suppressed or unsupressed, right out of the box. All our issued work guns are Colt 11.5" guns. They all run without a hitch either. Cant say one is better than the other, although on paper, the 11.5 is supposed to be better. Since the colt factory settled on that length, I assume a lot of GOV funds and testing were expended to find the sweet spot barrel length.

I would stay away from 8.5" you see on line. It may run, but most cans wont warranty for that short, and its a ear buster without the can. Also, you are trying to unlock the bolt when pressure is still WAY high. 10.5" is the shortest I would go in 5.56. If you want shorter, go .300 or 9mm...

[flux]

I am of the 10.3 sentiment, and wouldn't waste too much time monkeying with springs, buffers, etc. I'd get an adjustable gas block (infinitely adjustable, not the on/off type) and make sure the bolt locked back reliably with it cranked down as small as possible and be done.

When you say "terminal ballistics" you're going to have to provide more information about what you mean and what your personal requirements may be.

Effective out to 100 yards I'd be happy, while not common ,it may come along on trips to the game farm and do night duty there.

[Sero Sed Serio]

I did a lot of research before buying my SBR, an unsuppressed 6933, and it seems like 11.5" is the sweet spot for reliability/handling. Going down to 10.5" or lower drastically reduces dwell time which, (as I understand it) shortens the "reliability window" of the entire system. Not sure what brands you have access to, but if I were doing a DI suppressed SBR I would look hard at a BCM 11.5 upper with the thicker barrel or Daniel Defense DDM4V4S. I wouldn't go with a pencil barrel due to the weight of the suppressor hanging off the end, which affects the lighter barrels more as they heat up.

Work under the assumption that an SBR AR with a can is going to be similar in size to a 16" rifle.

[bravo7]

I run a WOA 10.5" suppressed and unsuppressed and it works quite well and I haven't experienced issues at all.

[Gray222]

I've gone really short - 7.75" and 14.5" - then settled in the middle at 10.3" with a MK18 DD contractor over-run barrel - you'll find these come up for sale once in a while (or you can just order one from them direct).

It is a fantastic barrel that is very accurate and does the job I need it a suppressed gun to do.

[flux]

What am I giving up or compromising running a 10 or 11" barrel? Anything else I should know running a suppressed AR.
I do like suppressors, I never shoot my bolt action without a suppressor on.

[Unobtanium]

I'm in the 14.5+mini can camp. I've owned multiple 10.x" guns, too. Sold the uppers.

[ragnar_d]

As stated above, 10.5-11.5. My personal preference is 11.5. With the right can, you'll be at or around the same OAL as a 16" gun.

[ASH556]

My preference is 10.3. SBR's and suppressors aren't black magic. It really just comes down to understanding gas port sizing. The MK18/CQBR is a proven system. 10.3" barrel, 0.70 gas port, H2 buffer, shoot suppressed or unsuppressed. My current upper is built on a Colt SOCOM barrel I had cut to 10.3 and the gas port opened up. You can find barrels made to similar specs. The biggest problem folks have with SBR's is that too may manufacturers think they need Jenna Jameson sized gas ports.

The 10.3 + suppressor comes in right at the same length as 14.5" without.

[SLG]

Flux,

To address compromises - I use an 11.5 at work, but favor the 14.5. Depending on ammo, you either give up a little or a lot of external and terminal ballistics. I've also found the 14.5 to run better, longer, suppressed than the shorter lengths, but I have extensive experience with only the SF cans in this regard. Maybe others are different, depending on the amount of back presure they have.

[JSGlock34]

I run a M4-2000 on a BCM 11.5" upper and I've found this combination will run reliably. I'll note that I tried to use the same suppressor on a 10.5" Noveske MK18 upper, and had numerous problems as the Noveske was over gassed. I have a Colt 10.3" upper lying around that I may try in the future.

I'm not familiar with the ASE suppressors or their muzzle devices, but note that barrel length, handguards, and muzzle devices can combine to render some suppressor-upper combinations incompatible (such as AAC cans on 10.3" MK18 uppers with the DD RISII).

[ASH556]

My preference is 10.3. SBR's and suppressors aren't black magic. It really just comes down to understanding gas port sizing. The MK18/CQBR is a proven system. 10.3" barrel, 0.70 gas port, H2 buffer, shoot suppressed or unsuppressed. My current upper is built on a Colt SOCOM barrel I had cut to 10.3 and the gas port opened up. You can find barrels made to similar specs. The biggest problem folks have with SBR's is that too may manufacturers think they need Jenna Jameson sized gas ports.

The 10.3 + suppressor comes in right at the same length as 14.5" without.

Typo above: that should be 0.070" gas port.

[flux]

Flux,

To address compromises - I use an 11.5 at work, but favor the 14.5. Depending on ammo, you either give up a little or a lot of external and terminal ballistics. I've also found the 14.5 to run better, longer, suppressed than the shorter lengths, but I have extensive experience with only the SF cans in this regard. Maybe others are different, depending on the amount of back presure they have.

I'm actually considering suppressing the 14.5", but no idea what effect it will have on the handling and balance of the rifle.
http://www.aseutra.fi/jet-z-cqb-bl-and-jet-z-cqbs-bl-suppressor

[SLG]

There's no question shorter barrels feel better with cans than longer barrels. I'm just a big fan of the 14.5"

[bravo7]

I think a 14.5 handles just fine and I run Specwar556s and even Saker762s on them. I also run those same cans on all my SBRs as well. Different tools for different jobs.