Shortest reasonable Barrel length 308AR

[polydeuces]

Just saw a really good deal on an apparently really decent 308 barrel.
Thinking of getting it and chopped it really short - mainly for ease of handling, understanding that it really does not affect accuracy.

Read this (http://www.thetruthaboutguns.com/2014/01/daniel-zimmerman/practical-applications-short-barreled-precision-rifle/) and now i am really tempted to go to like 13.5 or something like that - but definitely no more than 16".
Is he onto something?
I started reloading so that would be something i could load for.
With an adjustable gasblock and AR1-/A5 RE, reliability and getting it to shoot 'soft' is somewhat of a non-issue.

Anyone else shooting13"-16" barreled 308AR love to get your input.
THX.

[4thPointOfContact]

I have a 14" barrel on my Ishpore 2A1 'psuedo-scout' in 7.62 with a FAL flash suppressor permanently attached on the end. It's definitely loud but more than that it's handy and you never know when you may need to bayonet an armadillo.

RifleShooter.com did a test whereby they shortened a barrel from 28 to 1`6.5 in 1in increments, test results (http://rifleshooter.com/2014/12/308-winchester-7-62x51mm-nato-barrel-length-versus-velocity-28-to-16-5/)
33883
You should be able to extrapolate from that.

Final results averaged less than 25fps loss per inch. Count it as 30 to be safe and judge if it's worthwhile or not.

[jbjh]

I have a 14" barrel on my Ishpore 2A1 'psuedo-scout' in 7.62 with a FAL flash suppressor permanently attached on the end.

Pics man! Pics!!


Sent from 80ms in the future
Much peace
Jimmy

[SomeOtherGuy]

If you go that route, do not, do not, do not put a muzzle brake on it. A 14.5" .308 with a two port brake is the loudest and most unpleasant thing I've ever shot, including 50 BMG rifles, magnum handguns, etc.

[4thPointOfContact]

I'd love to say, "Oh, you are soooo wrong!"... but honestly, Ya right, it is dang loud (but at least it's a legal length).

[Benito]

If you go that route, do not, do not, do not put a muzzle brake on it. A 14.5" .308 with a two port brake is the loudest and most unpleasant thing I've ever shot, including 50 BMG rifles, magnum handguns, etc.

I second that.
I shot a 13.5" LMT MWS with a muzzle break a few years back, and distinctly remember not only the crazy noise and concussion, but the gas in my face. It was enough to make me cough and sting my eyes even with shooting glasses on.

[MegademiC]

With the loss of velocity, I don't see the benefit past the cool factor. Of course ammo cost can change the decision, but I would opt for a 6.8 or another caliber for a barrel that short.

What do you want the gun to do, what's it's purpose?

[polydeuces]

Was familiar with those barrel length/velocity loss test-numbers, thanks - clearly the loss of velocity is a non-issue.

And comps can be an issue in company (or to self) - check. Thx!

'What do you want it to do' is always the main question: Fast, light, devastating effective up to 300 yds., moa accurate.
Run it with a RDS or 1-4 optic for hitting stuff 2-300 yds and in. NOT a precision rig. (For anything past that I can go with my 18")
Approach the balance and portability of a 16" AR15.

It's been said here by real SME's 16" is really plenty for AR308, I understand now why.
More I shoot 18" more I realize there's nothing manageable about it comparing with an AR15/M4 once you get off the prone.
However stripped, no glass, bi-pod, its actually quite light, got me thinking go with a 14" barrel and slick rail may do the trick.

My main question is how much further I can push it until there's 'diminished return'- who has experience with this.
The 'review' I added seemed rather convincing about the 13.5" but I'd like a bit more real world input.

fwiw - I like the .308 caliber, not interested in 6.8 or 300 blk, 338 lapua, 300WM etc. - don't want to/need to add one more caliber to the mix. If I ever exceed the capability of my gear - maybe. That won't happen any time soon if ever.

[caporider]

I've owned a metric shit ton of .308ARs from 14.5" to 22" in barrel length. IMHO the sweet spot is 16" or thereabouts to balance handling, reliability, and bullet performance. Long distance shooters are migrating to 6.5 Creedmoor or similar rounds, so if you want to chase top shooters out past 1000 yards you would not use .308 anyway -- which IMHO negates the need to build a 22" or even a 20" .308AR.

Shooters with 12.5" .308s as well as those with 22" .308s are trying to cover the more esoteric edges of the .308AR performance envelope. The whole huge area in between these two extremes is very effectively covered by a 16" .308AR shooting modern ammo.

[tom12.7]

I've owned a metric shit ton of .308ARs from 14.5" to 22" in barrel length. IMHO the sweet spot is 16" or thereabouts to balance handling, reliability, and bullet performance. Long distance shooters are migrating to 6.5 Creedmoor or similar rounds, so if you want to chase top shooters out past 1000 yards you would not use .308 anyway -- which IMHO negates the need to build a 22" or even a 20" .308AR.

Shooters with 12.5" .308s as well as those with 22" .308s are trying to cover the more esoteric edges of the .308AR performance envelope. The whole huge area in between these two extremes is very effectively covered by a 16" .308AR shooting modern ammo.

I pretty much agree, 16" covers the bases pretty well. Going shorter than 14.5" is setting yourself for other issues, longer than 18" provides little gains for the majority in the context that we are referring to. Going shorter than 14.5" to 13.5" seems like a much larger jump in flash and blast by a fair margin than going from 16" to 14.5" that can cause issues itself. The gain going to 20" from 18" doesn't seem as much as going from 16" to 18" when you look at the system as a whole. Some bolt guns are 32", but they are made so specific to an application that it is useless in anything but that.

[Benito]

There are some great sources out there for decisions on barrel length, including specifically for .308.
I went with a 16". Lengths above that will squeeze every last bit of velocity out of the cartridge, but it's up to you and your needs/wants if that juice is worth the added weight and overall length.
Going shorter that 16" will increase muzzle blast quite a bit.
With a semi-auto, there are cycling dynamics/timing issues to consider, which I am not qualified to discuss, that are not present in bolt guns.

http://rifleshooter.com/2014/12/308-winchester-7-62x51mm-nato-barrel-length-versus-velocity-28-to-16-5/

http://www.thetruthaboutguns.com/2013/10/daniel-zimmerman/the-truth-about-barrel-length-muzzle-velocity-and-accuracy/

[LS1POWERED]

Taken from an archived thread on the other site.


150g HPBT win 748 loaded to chamber pressure of 56.4k, a warm load.


16" barrel, 12k PSI, 97% powder burn
2623 fps with 2291 lb/ft energy.*


12" barrel 16.7k PSI, 94% powder burn.
2417 fps with 1946 lb/ft energy.


10" barrel 20.5k PSI, 91% powder burn.*
2273 fps with 1720 lb/ft energy.


8" barrel 26k psi with 87% powder burn
2080 fps with 1441 lb/ft energy.*


So either barrel length you are looking at will be effective, not loosing a ton of velocity going to a 12". Heck even the 8" barrel is comparable to a 16" 300 blackout or 7.62x39. Plus short guns are more fun.

[the_1iviper]

i have a 12.5" 308 that's a great shooter. it's no more of a flamethrower/hand cannon than any of my 5.56 sbr's. the gun and ammo are much heavier than it's smaller brother but it also makes bigger holes through heavier/thicker objects than 5.56 will. i mostly shoot m80 ball for general blasting but i've found that mk319 mod0 does really well out of a short 308. trying to push the heavier bullets at distance is where you would want that extra couple of inches of barrel imho. i think lmt and h&k and a few others have hit the sweet spot on a short 308 with their 13.5" barreled offerings.

[Failure2Stop]

With modern ammo and contemporary 7.62 semi-auto technology, I'm good down to 14.5, if the range envelope is inside 600 meters.
Go to a 1:8 or faster twist, and that stretches a bit, but the trans-sonic range is what it is.
With anything less than 14.5 you start to get really close to .300 Blk performance, at a noticeable increase in burden with 2/3 ammo capacity.
I personally like 16" 7.62 as it covers a lot of ground acceptably, not outstandingly.
Reducing MV also gets into whole new areas of zeroing concepts with a 7.62. 16" .308 guns already benefit from a departure in conventional zeroing approaches (I'm going to do a little write-up on that soon).
The difference in wind when going from a 20" to a 16" is noticeable, losing even more starts to get annoying at around 300.

Really it all comes down to meeting expectation and requirements. If you know what you are getting into, I'm not going to tell you not to do it.

[Amur]

With modern ammo and contemporary 7.62 semi-auto technology, I'm good down to 14.5, if the range envelope is inside 600 meters.
Go to a 1:8 or faster twist, and that stretches a bit, but the trans-sonic range is what it is.
With anything less than 14.5 you start to get really close to .300 Blk performance, at a noticeable increase in burden with 2/3 ammo capacity.
I personally like 16" 7.62 as it covers a lot of ground acceptably, not outstandingly.
Reducing MV also gets into whole new areas of zeroing concepts with a 7.62. 16" .308 guns already benefit from a departure in conventional zeroing approaches (I'm going to do a little write-up on that soon).
The difference in wind when going from a 20" to a 16" is noticeable, losing even more starts to get annoying at around 300.

Really it all comes down to meeting expectation and requirements. If you know what you are getting into, I'm not going to tell you not to do it.

Jack, how about you get me one of those 14.5" DIrect attach DSR kac sr25 and we just call it a day. :cool::laugh:

That seems like the rig right there from 0-600 for anything you want to do.

[polydeuces]

The key issue here, as always indeed, expectations and requirements.
Knowing full and well that less than 16 is getting into an area where compromises will be made at longer ranges.
Less than 13.5 - 14 and things get a bit more 'experimental' not just range but performance.
Guess it's all about the doing it.

See - here's the thing. With AR15 we have every (in)conceivable length.
Not so with AR308.
So we're simply going to have to do it ourselves and share the warmth. Simple as that.

IF.... I had a more 'dynamic" budget, I'd start with a 16" barrel, test, chop it to 14 and compare them.
One thing I've learned about the AR platform is (speaking for myself) with quality components it usually out-performs me, and is capable of things its said not to be.

Clearly a 16 will be GTG - then seeing a decent barrel (http://aimsurplus.com/product.aspx?item=XLSK30818&name=LOSOK+Black+Nitride+7.62+NATO+%28.308%2f7.62x51%29+18+in.+Barrel&groupid=2532) will set me back 'only' about $140, and it won't be a crime beating it up a bit.
Dedicated receiver (aero) ~$95. Shipping barrel to adco, chop to 14.5 crown n thread another ~$60.

It's just numbers right? And I can't take it with me - none of it. Keep talking, I'm almost there.

[Stengun]

Howdy,

Very interesting thread.

Most of the "old school" reloading manuals usually suggest 25 ft/sec per inch of barrel for loads below 3,000 ft/sec and about 30 ft/sec for loads above 3,000 ft/sec.

As clearly shown by the test on the link someone provided that factory loads designed to work best in a 24" barrel had did their thing by 28".

For a barrel longer that 26" a handloaded would use a slower powder and for a shorter barrel, especially 16" or less a faster powder would provide better velocity than a powder that would function best in a 24" barrel.

Also for a short barrel a faster powder would create a smaller fireball blast and muzzle blast.

Paul