Gas/Buffer System Help .300 AAC Pistol

[hooky]

I've got a 12" .300 AAC upper coming for a pistol build. Any advice or a resource to figure out the gas and buffer systems? I seem to be able find lots of info on 5.56, but struggling with clear advice on a 300. I'm hoping to figure out what I need to take into account in order to balance both a subsonic and supersonic load with the correct buffer and gas system so it will cycle reliably. Hopefully, I'm not overthinking it.

Thanks in advance.

 

[jinks]

If it is an assembled upper, the gas system is already installed. It may be the standard pistol length as the pig-tail is usually used only on shorter barrels. For the buffer start with the standard carbine buffer and only go heavier if needed.

 

[jblomenberg16]

Jinks is spot on. YOu will mote likely have a pistol length gas system on it, and working your way up in buffer weight will be the way to go. I have a 10.5" with a spikes ST2 that runs well on subs and supers. What size is the gas port on your upper, or is it listed? That is probably as much of a variable as anything.

 

[hooky]

.750 gas block and it does have a pistol length gas system.

I wasn't sure if I needed to play with gas block to make it work and/or if I needed to worry about the buffer. Assuming the .750 is the OK, sounds like I'm probably good to go and probably am over thinking it.

 

[bmbutch]

8.5" with Spikes St2, did have to upgrade extractor spring, used BCM upgrade kit, now runs great sub w/ suppressor or super w/o.

 

[throttletony]

If it is an assembled upper, the gas system is already installed. It may be the standard pistol length as the pig-tail is usually used only on shorter barrels. For the buffer start with the standard carbine buffer and only go heavier if needed.

Jinks is spot on. YOu will mote likely have a pistol length gas system on it, and working your way up in buffer weight will be the way to go. I have a 10.5" with a spikes ST2 that runs well on subs and supers. What size is the gas port on your upper, or is it listed? That is probably as much of a variable as anything.

What they said. It should likely run well from the beginning. Use carbine buffer, and adjust from there.
Also - they were asking about the size (diameter) of the gas port (HOLE). You can also look into getting an adjustable gas block, but with the right buffer you should be in good shape.
The beauty of the 300 blackout is that it *should* run equally well suppressed/unsuppressed and sub/supersonic.
Buying an assembled upper from a competent manufacturer is already a good step

P.s. Tell us about the lower you're putting it on? I'm assuming a pistol lower? Are you going to be using a SB15 brace? Just curious

 

[hooky]

It doesn't list the diameter of the the actual port, just the block.

It's going onto an Anderson lower that I haven't begun to build yet. Undecided on the Sig pistol brace, but I'm leaning that way at the moment.