I’m in the process of putting together a .308 SBR to run subsonic and suppressed. Anybody know whose making 10.5" barrels with 1:7 twist rate?
Why???
The ballistics of a .308 under 16" simply don’t make sense.
Get a .300BLK (especially if you want subsonic & suppressed)
I’m assuming you mean 300blk? 308 is going to be difficult to “run” in subsonic, unless it’s a bolt gun. Velocity out of a 300blk can’t be much more than a 300blk, but I’d be interested in hard numbers.
One of these might be what you are looking for…
300 Blackout 10.5" http://www.shop.blackholeweaponry.com/300-Blackout-caliber-105-length-AR15-300BO-105.htm
.308 10.5" http://www.shop.blackholeweaponry.com/308-Win-308B-caliber-105-length-AR10-308-105.htm
I already have 3 300 blackouts. I want to build a gun that has similar subsonic characteristics running 200+ grain ammo but also has the supersonic performance of a .308. The ballistics out of a sub 16" .308 barrel will simply be a little slower than that of a longer barrel.
It will be single shot with sub sonics. You could drill out the gas port to MAYBE make it cycle but it would be ridiculously over gassed.
If you use 220 gr. A-Max’s or 230 gr. Bergers with a low mass carrier it should cycle, especially with a pistol length gas port. Drilling out the gas port would be a last resort but overgassing could easily be fixed with an adjustable gas block.
Listen to yourself talk. A pistol length DI gas system on an AR-10 style rifle running .308. That would be over pressured for sure. The route your going will be a subsonic only setup. A 220 gr bullet traveling subsonic, dosent matter if it’s fired from a 308 or 300 blk, will have the same energy either way. It’s your build so do as you please.
Easy all.
It’s a question about source, not practicality. If you aren’t answering the question, please move along.
From Tapatalk:
Jack
Wearing Moderator hat.
Hence the adjustable gas block. Overgasing solved. And the whole point is to have a gun that has the same subsonic ballistics as a 300 blackout but with the increased supersonic performance of the 308. Dont see whats so bizarre about that.
Tagged for interest. Although I’m also curious about the practicality of what you’re suggesting, I’d be interested in seeing how it turns out. Hope you post an update when your build is done and tested. Good luck.
Testing has shown that it’s not that great to go below 12" for. 308 barrels as things drop off sharply after that so I’d consider that a good minimum. As for using an adjustable gas block on a pistol system, it would drop the amount of gas in the system but it won’t drop pressure. You have to worry about multiple factors such as dwell time, back pressure, the quantity of gas, chamber pressure, barrel pressure at different points, etc. and there all effected by different things. An adjustable gas block is only a small part of the equation and won’t be able to deal with everything combined on a pistol system running full power loads.
Sent from my SM-G900T using Xparent BlueTapatalk 2