Subsonic, semiautomatic suppressed .308/7.62 pistol or AR platform.

[just bill]

I like the idea of subsonic semiautomatic weapons. The only way I have found to utilise .308/7.62 projectiles is with a 300 blackout. Most all subsonic rifles will not function in the semiautomatic mode due to lack of pressure. Is there a .308/7.62 pistol that can function subsonic semiautomatic suppressed?

Thanks,
Bill

[Tackleberry41]

Probably not, you do need pressure to cycle a gas operated weapon. The black out gets that pressure thru the type of powder used. A 308 you have so much more case capacity, it would not be easy to find a subsonic load that would still cycle the weapon. I have messed with alot of subsonic, I can get em pretty quiet. But using small amounts of fast burning pistol powders, in bolt action or single shot weapons. No way any of them would come close to cycling a gas gun. Its why the blackout has caught on, you can get a weapon that will work with super and subsonic ammo.

[runfiverun]

airc there were some 30 carbine pistols made waaay back when, I'd bet that they are set-up to bleed off the excess pressure, or are a blow-back design.

[HATCH]

it can be done.
You would end up with a weapon that is dedicated to shooting only subsonics for 308
the BCG would have to be lightened
the gas port be increased.
you would also run a different buffer and buffer spring.

[just bill]

it can be done.
You would end up with a weapon that is dedicated to shooting only subsonics for 308
the BCG would have to be lightened
the gas port be increased.
you would also run a different buffer and buffer spring.

That sounds ok, I have enough .308's in the normal operating range. Are you talking AR platform? I just think it would be great to have a suppressed semi automatic, that functions semi. Where would I start?
Bill

[dilly]

I would hate to beat a dead horse but subsonic 30 caliber bullets are much more efficiently done in 300 blackout. You could underload 308 win (or 7.62x51) all day and maybe tweak a gas system to make it work, but that's what 300 blackout was designed to do. All the extra cost and mass of the AR10 type system will just be extra weight, and your brass will be more expensive (at least compared to if you convert your own). It will be cheaper, smaller, lighter and easier to come by. It's available readily in handgun configuration.

What you're doing is the equivalent of trying to find a 45 win mag LAR Grizzly, load it with 230gr bullets and shoot them subsonically. Why do that when you could easily have a 45 ACP that is better suited in every way?

If you get anything in 308 win you will have to modify it to cycle subsonic ammunition. If you get it in 300 blackout you might, but shouldn't have to do so. The modifications would be basically the same.

Okay, with that said I wanted to say if that's what you want to do it's your right and you can do whatever you want with your money. I hope you enjoy the build either way. Looking back that came off almost as a rant, and I'm sorry for that.

[just bill]

I would hate to beat a dead horse but subsonic 30 caliber bullets are much more efficiently done in 300 blackout. You could underload 308 win (or 7.62x51) all day and maybe tweak a gas system to make it work, but that's what 300 blackout was designed to do. All the extra cost and mass of the AR10 type system will just be extra weight, and your brass will be more expensive (at least compared to if you convert your own). It will be cheaper, smaller, lighter and easier to come by. It's available readily in handgun configuration.

What you're doing is the equivalent of trying to find a 45 win mag LAR Grizzly, load it with 230gr bullets and shoot them subsonically. Why do that when you could easily have a 45 ACP that is better suited in every way?

If you get anything in 308 win you will have to modify it to cycle subsonic ammunition. If you get it in 300 blackout you might, but shouldn't have to do so. The modifications would be basically the same.

Okay, with that said I wanted to say if that's what you want to do it's your right and you can do whatever you want with your money. I hope you enjoy the build either way. Looking back that came off almost as a rant, and I'm sorry for that.

Thanks, I am just playing with an idea. The 300 bo has the right stuff and an upper can be added to my .458 conveniently, I just trying to explore all options for the .308 before I jump into another caliber. I have a huge amount of 7.62 and wanted to just explore its outer limits.
Thanks
Bill

[HATCH]

300bo is really the way to go for subsonics
The only difference between a 223 ar and a 300bo ar is the barrel itself.
Mags are the same.
With 308 it's going to be total r&d to figure out what works for ammo and the gun settings itself

[xacex]

If you just want to play with subsonics and a can the 9mm AR pistol is also an option. It gets more play time than the 300 BLK pistol just because I can use red dot, and it is super cheap to shoot. I use 3 grains of red dot behind a Mihec 359-125 h/p in a 10.5" upper and it is subsonic, but will still penetrate 2 water jugs before damaging the third with full expansion at 25 yards. Now, it is not a 100 yarder like you can do easily with the blackout, but once you have your scope adjusted it is no problem ringing steel at 100 with it. Barrels and bolts are cheap now on ebay, and I have some tricks to make the cheap magpro block work great, and be removable without having to take off the bolt catch.

[wordsmith]

300bo is really the way to go for subsonics
The only difference between a 223 ar and a 300bo ar is the barrel itself.
Mags are the same.
With 308 it's going to be total r&d to figure out what works for ammo and the gun settings itself

Right on Hatch. I've been researching / troubleshooting subsonics in 308 and 300 BLK for probably a couple of years now, both target and hunting bullets, and the 300 BLK is the only option in my book for semi-autos. Sub's in 308 bolts are a lot of fun with Trailboss (1 MOA accuracy possible), but outside that powder, life is very difficult in 308 subs. A cycling 308 subsonic AR would be an interesting case study, and is possible, but not practical or useful beyond that single purpose as others have mentioned.