I started to post this in the Silencer section, but it's really about 308 barrels, so here I am.

Every time I "finish" one project (finish in quotes because none of my guns are ever finished...) I come up with an idea for my next project.

I decided that when the Black Friday/Cyber Monday sales hit this year I want to build a 308 AR.  I had originally thought of a 20" or 22" barrel, but I plan on hanging a Specwar 762 off the end.  For those not familiar, the Specwar 762 is 9" long and weighs 24oz.  It's a tank, and I couldn't be happier with it on my 5.56 and 300 Blackout SBRs, and would like to use it on a 308 AR as well.

I got to thinking about hanging that much weight off the end of the barrel, and started to worry that 20" or 22" would have too much flex.  I've been looking into articles and forum posts about barrel length affect on velocity, distance, etc.  I started looking at barrels, and quite honestly, got kind of overwhelmed (gas length, material, profile, etc.).  I'm sure several of you have gone though this same process, so I was hoping to draw on your experiences.

When hanging a pound and a half off the end of a barrel, is it better to go shorter for less flex, or will a longer barrel with the right material/profile give the same results?  Ballistic Advantage has a 20" bull barrel that I'm looking at now, but at 69oz, wow.  If a shorter barrel or a different profile would react the same to the additional weight being added with the can, but with less weight and negligible velocity loss, I would lean that way.  There has to be some sweet spot where you get decent velocity, less flex with can added, and the barrel is not unnecessarily heavy.

What are some barrels that you are using with a can that you are happy with?  Any mistakes you have made that I can learn from?

Thanks!

not sure where you'd find it but one attribute aside from ammo availability with the .308 is it does well in short barrels. if I were to run 20+" barrel i'd step up (or is it down?) to a 6.5 creedmoor.

that being said i'd go with a 16" or a pinned welded what ever length works with your muzzle device. then go with a spr ish profile if not a hair lighter. I would then go with a midlength gas (unless you end up going sbr territor )

Now finding this exact setup may be difficult however gm rifle barrels is now selling pre-chambered .308 barrels that have no gas ports and are straight bulls essentially. you could then have a gunsmith or adco make it into what ever you want. I personally wouldn't go much below .700" under the guards if your wanting to do sustained distance shooting, if not you could go a little lighter.

Edit: well I just went to get you the link of the barrel mentioned and realized it has a 11.25" twist. this would be a deal breaker for me. I like to sling the heavies 175+ so a 1:10 or 1:9 would be more ideal in that situation. here it is anyways. http://www.gmriflebarrel.com/gm-b9-21-x-1-308-win-chambered-blank-barrel-stainless/

Thanks for the replies!

I'm not going to SBR this one (the govt has enough $200 donations from me for a while) so I'm looking at 16" or longer barrels.  I'm just trying to figure out the best compromise - a barrel long enough to keep velocity, but short enough not to flex too much with a can on the end.

I have a 20” medium weight barrel from Armalite (.308) that I used to run with an SAS stainless can that came in at around 24 oz. Other than being very front heavy, it was fine. I only had a 1.5 moa adjustment between my normal zero and suppressed zero.

The Specwar is the same weight, so that gives me a good idea of what to expect.

Thanks!