How short can you go with 7.62/.308 before you get serious ballistic issues? I know LWRC made the REPR with a 12" barrel, but can’t you go any shorter than that? If not with a DGI-style system, what about with a piston?
Thanks.
Why would you want to?
Why turn a .308 into a belly gun? I think you’d be better off doing a 5.56 or .300 Blackout SBR.
because the 7.62 has more kinetic energy and penetration.
I fail to see where chopped down .308 is going to be any more effective than a .300blk (especially out of a barrel under 12"s)
The SCAR-17 has a 13.8 inch barrel. They make special rounds for the shorter .308 like the Mk319.
It wont 300blk bullet weights are right on par with 7.62 as they are both 30 cal bullets. With velocity lost by shortening the 7.62 barrel its pretty much a moot point. I was at one point when I was fairly green on it looking into buying a 12" barrel 308. I talked myself out of it and decided to go with a short 5.56. When I eventually do pick up a 7.62 it will be a precision rig much like that of offerings from KAC. The way I see it is why waste the rounds potential and what its best at.
As far as 338 lapua I’m not even sure why you would want that in an AR platform at all. Especially at around five dollars a round. If you want to try it out as it was intented pick yourself up a savage BAK10 tactical. Super smooth rifle and by far the best bang for your buck out to a thousand right now. Like I’ve said before though and like many others will tell you. Your equipment isnt the most expensive part of shooting if you actually get out there. Its ammo.
Can you give us some kind of a clue what you mean by “serious ballistic issues”?
I guess I can see why one would be interested with the 7.62, but somewhere around 13.5" would be my limit though I have yet to find an application for it. The blast that comes with it will get offensive and you’ll start loosing a lot of velocity. For me, I can’t see going any shorter than 14.5" though 16" is where I’d like to stay. I thought about SBR’ing my SCAR H (13.5"), but it just seems silly to do for my needs.
There are plenty of rounds better suited for short barrels. I’ve fired short barreled 5.56 and 6.8 rifles in confined spaces. I don’t think I’d want to do that with an 11.5" 7.62x51.
Dude, the Scar heavy is either being ran with delinked 147gr ball or 173gr OTM. Neither of these rd’s are special. I have shot the SCAR Heavy while in A-stan last summer, and worked along side an 18B who carried it on every mission. There is no “special scar ammo”
Before you buy anything, do more research. You will save yourself money and frustration.
Signed,
Joseph
While it may not be “special SCAR ammo”, mk 319 was optimized for shorter barrels.
And that still doesn’t make it “special scar ammo”. FYI: I did not see any MK319 ammo while downrange, but I never bothered to ask the Navsoc or Marsoc guys either. I did see plenty of M855A1 and MK262 ammo though.
I don’t really know how relevant what you saw down range is to this discussion as i’m fairly certain 319 is accessible on the market. I do understand your thinking tho. As far as 338 goes its most certainly replaces ranger battalions and SF’s 300s winmags quite well. I’ve personally put a few deer to rest at 900m. Filling doe tags believe it or not. I do agree that they fill somewhat of an anti material role as well.
I am not arguing as to whether MK 319 ammo is even available or not, because I feel certain that someone is engaging hostiles with it, I am saying that even the SOF guys aren’t swimming in this particular ammo, at least not yet.
C-Grunt, go back to the drawing board. Decide what your personal operational needs/wants are, then start researching platforms/calibers that will likely serve your intended purposes.
Signed,
Joseph
Right on brother. Sorry if it seemed I was questioning anything. I was agreeing with you but putting a little further insight into it if that makes sense. Either way i’m not really up for any more insight to this thread. You can leaf a horse to water ya know. Its up to him now.
For .308, the shortest barrel I like is 16". Most military guys I know running Mk17’s have chosen to go with the 16" barrels. Generally 150-155 gr works better in a 16" than 130 gr or 175 gr. When you start talking really short .30 cal barrels, you might as well run .300 BLK as performance is very close, but without the blast, flash, and weight.
Todd Hodnett has reportedly used .338 Lap Mag in 20" 1/9.35 twist barrels and was still able to accurately reach out to 2000m…
I would personally consider 900 feet a long shot. But that’s just me. After all, I’ve only been doing this for 40 years.
I should mention that i’m from and currently living in South Dakota. I would highly doubt anyone finding that much open space in NC.
The ~150gr class seems to be a more optimal balance of variables in my 16"-18" .308s. I prefer the Federal 308A in a soft point and the BH Gold 155 AMAX. Quality loadings of the 150 Nosler BT work well too.
I would recommend against an SBR 308 AR, or CQB type gun. Unless you just want to do it to do it. Which is what I did. I like it, but honestly I am probably going to move away from it, and maybe see if I can get some money back out of the Leonidas project.
The HK51 is silly, but fun as hell!!! Especially when someone owns a trigger pack. 
The 11" Para FAL is a nicely balance package, but still heavy and still impractical.
I can’t comment on a SCAR-17, as I’ve only ever handled a full size version, but I can’t imagine it’s much different.
In retrospect, I should have gotten a 6.8SPC at the time, or now a 300 Blackout, as the ballistics of a 12" 7.62 NATO are about on par with a supersonic 300BLK. Maybe a little better, but at a huge weight penalty. HUGE!!