Looking at playing with subs in my G2 and just wondering what the heaviest I can shoot would be.  Twist is 1:10 w/chrome lining.  I'd be looking at using it for cull deer (ag tags).  

I realize it will be a one shot wonder, but that's fine.  I have a dedicated 9mm AR with F1 suppressor for a repeater target and fun work.  If I like it enough, I might build a 300 AAC upper, but for now, I'll just play with the 308.

Have no idea how they would work on deer.. but maybe these?  http://makerbullets.com/proddetail.php?prod=308180SBLK

Or if you want heavier, then these.. but they won't expand any.. https://www.midwayusa.com/product/348088/hornady-interlock-bullets-30-caliber-308-diameter-220-grain-round-nose-box-of-100

Prob have to be a brain cage or spine shot to drop em DRT, otherwise you could be in for a tracking adventure...

& FWIW, 11.5gr of Trail Boss gives me about 1060fps with the 220gr Hornady out of my .308 SA (16").

I'm asking this from a strictly "wanna know" perspective.  This year I finally got into the 300BO with a 9.5" BA barreled pistol build for suppressor use only.  My best developed load ended up using a Hornady 208g ELD-M...the match instead of hunting bullet because expansion with 300BO suppressed/subsonic is pretty much a moot point, so accuracy being the priority.

I'm also an AR10 shooter, got a pair of them...20" and 16".  My question is this for those who have really pursued subsonic .308 in an AR platform.  Since .308 subsonic and 300BO subsonic both use a 30-cal bullet that is going to be kept below the speed of sound, is there any advantage to using the heavier, more complex, more expensive .308 AR platform?  It seems like the lighter weight, shorter barrel, more affordable 300BO would be way more desirable.  After all the 300BO was designed exactly for this role.

Again, I've only done the subsonic suppressed deal with my 300BO for 30-cal.  I'd just like to hear discussion about the comparison of the two.  Oh...I'll add that I have no desire to hunt actual "game" animals with my 300BO...just varmints, pigs, coyotes, or ne'er-do-wells...for which I'm not as concerned about ethical dispatch.

That's a good question. I'm curious about this as well.

My guess is there's no advantage to .308 if you're still pushing a 30 cal bullet at the exact same speed.

At a loss to understand the question..?
They are identical from a ballistics POV and A .308AR  is no more complicated than a .300blkout AR.
If you want to shoot subsonic .30 cal bullets in a semi auto AR style with reliability of function you go .300blkout.

I originally asked about a .308 1:10 twist, not 300 blackout with 1:7.  I don't have an AAC and probably won't for some time, so I don't care about 300 information at this time.

I also realize my 308 will not cycle these rounds, but again, I don't care at this time.  I just want to try it out and I don't have an issue not having a second shot readily available.

So, what is the heaviest bullet that will stabilize in a 1:10 twist at sub sonic velocities?

I would defend anyone's pursuit of just about any caliber, gun, etc. because it's their business even if it's just for fun.  I'll differ with your comment about complication.  The .308 and similar bigger caliber AR platforms have quite of bit propriety and gas control issues.  That's not to say that those issues cannot be overcome, but I think it is at least a slight complication issue over 300BO.  

The 300BO is extremely simplified by having almost total interchangeability with everything AR15...almost.  With today's prices I'm seeing on parts, complete uppers, etc. for 300BO and other AR15 platforms, I wouldn't pursue .308 subsonic/suppressed.

Still, I wouldn't poo-poo your goal.  If enough details are available, I might even try it for grins since I reload and have a suppressor that will fit my AR10's.

I just worked up a subsonic load in my 18" 308 AR with these:

Bullets

Federal case, CCI 34, 10 grains of trailboss = 1016 average fps. With the gas fully closed they are quieter than my 300blk. I would never hunt with them since they won't expand.

From what I've read, the heavies that run well in 300blk like 220's won't stabilize in the 308 1:10 twist. The flat base helps with stabilization. Hope this helps.

The 220gr Hornady's I posted above stabilized just fine in my 16" 308AR going 1060fps... also, if you poke the info for the bullet into the JBM stability calculator it comes out just fine (bullet length is 1.25")..

You want heavier than 220gr?

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

Good to know. I'll have to try them out.

I started with "The Load" with a 173 gr. Meister cast bullet.  Shotgun patterns from my Ruger GSR.  I worked down to 6.0 grains of Red Dot and found a great load with velocities around 870fps.

I've since switched to 10.0 grains of TrailBoss with the same bullet.  Great groups, better ED/SD, velocity right around 1030fps.