300BLK gas system question

[Skunk]

All,

For those of you shooting 300BLK from an AR platform, what gas system length is best for 10.5-11.5" barrels with the intent to shoot strictly subsonic ammo, suppressed? And what buffer, etc?

Thanks.

 

[loveha]

Pistol, H2, maybe H3 depending on gas port size and if you are not utilizing an adjustable gas block.

 

[hafejd30]

Mine is psa lower/aero upper- Pistol Legth gas- 8” Barrel- 200 grain S&B Subsonics- TBAC Ultra 9

Only fired a couple boxes through it. Runs great. Very clean. Was surprised by how clean it stayed. My 308 even the brass ejects covered in soot with an adjustable gas block

 

[Skunk]

Probably just try to use a Geissele gas block. Just was unsure on choice between pistol and carbine length gas system. Thanks, guys.

 

[fancygunz]

Pistol, H2, maybe H3 depending on gas port size and if you are not utilizing an adjustable gas block.

I have an 8.3" with standard buffer. I can't cycle some heavier subsonic handloads with lower powder weights. Would changing the buffer help?

 

[loveha]

I have an 8.3" with standard buffer. I can't cycle some heavier subsonic handloads with lower powder weights. Would changing the buffer help?

If you have a standard buffer then no, increasing buffer weight would make things worse.
Without more rifle info it's hard to recommend any sort of corrective action.

 

[Yondering]

Probably just try to use a Geissele gas block. Just was unsure on choice between pistol and carbine length gas system. Thanks, guys.

It absolutely must be a pistol length gas system, there is no wiggle room there. A carbine system in that barrel length can be made to run with supersonics but not with subsonics as well.

Even in a 16" barrel, if you want good function with subsonics, you need a pistol length gas system.

With that said, with a pistol length gas system and everything set up correctly, it should run both supersonic and subsonic loads with no modifications or tuning changes.