Heavy bullets in a semi auto 308?

[mao0720]

I may be picking up an AR10 with a 16" barrel and would like to run medium to heavy bullets like 185-205gr range. I want to keep the retained mv and energy up for medium range (600-800yd) shooting. Is there any safety or function concern with running this heavy of a bullet in a semi auto?

 

[XTR]

I may be picking up an AR10 with a 16" barrel and would like to run medium to heavy bullets like 185-205gr range. I want to keep the retained mv and energy up for medium range (600-800yd) shooting. Is there any safety or function concern with running this heavy of a bullet in a semi auto?

You can probably do it but first of all 185 to 205 is heavy to super heavy for a 308, there is nothing medium about that. It may be what we run in F-TR but it's way beyond what anyone was envisioning when they designed the 308. The 185s and heavier are really designed to be seated way out beyond mag length, in F class we're typically seating them out to 3.00 and longer, seating them back at 2.8 or so to get them into a mag is really taking up a lot of space in the case and limiting what you can do and begging to blow something up if you start trying to use the load data we use with a bullet seated all the way up in the neck.

With a 16" barrel beyond 600 you are really stretching it. It can be done but I've watched the service rifle guys struggle at long range with short barreled 308s, it doesn't look particularly fun and it's not particularly accurate.



If I ever get an AR-10 type platform I'd limit it to what it's designed for, and launching heavies to 800 yards ain't it, at least not with a 16" barrel. I shoot a ton of them so I'm sure I'd probably have a load for the 185 Bergers, but I'd be far more inclined to run 168s, they are a great bullet to 600, or maybe clone the M118LR with 175SMKs but that would be it.

 

[mao0720]

I was wondering how much capacity the heavy bullets would take up. Id like to run as heavy as possible so i guess maybe 178gr and maybe 180-190smk. Ill just have to play around with it and see what I can do.

 

[hogan]

Like 175gr or even 168 isn't enough?

Got a 16" barrel on your 10. Maybe if you got a custom with a std rifle length gas tube or longer; but you don't. Gonna beat your brass to hell with the carbine length gas tube anyway... Not really much to be gained from the high BC heavy bullets. Can load 180gr Speer Grand Slam and other more compact designs, but there is no free-lunch for heavy high BC bullets in AR-10 world. Single loading with similar gas impulse powder charge, maybe. Not what you want though, is it?

180gr SMK is about the upper limit. The 178 A-max is another VLD design. Not friendly for magazine length loading is my guess, like the 75gr A-max in AR-15. If you have an Armalite or other factory barrel, the chamber is most likely reamed for the 168 matchking. 175smk usually work fine.

Not really thinking my AR-10 is a 1000 yard effective piece. Bolt rifle, that's another matter. 750/850yds is my idea of effective working range. With your 16" barrel more like 600yds; maybe. Kinda like the LT I recall commenting on the National Match board about wishing he had a 20" barrel instead of the shorty on the issued M4 so he could make hits reliably out past 350yds. Shorties leave much to be desired in real world rifle shooting situations...