Gas length on a 300 BO ?

[Old Corps 8541]

Seams all I see when hunting an 18" or 20" AR Bbl. in 300 BO are pistol or carbine length gas systems. My plan is to build something for the grand kids to shoot using my 180 - 200 gn cast. bullets. I'm figuring around 1100 FPS , No suppressor .
Thought I'd ask here before contacting a few that offer AR Bbl's about a longer gas system .

 

[TonyTheTiger]

Anything near subsonic is going to require a very short gas system. Think about it, you're basically shooting a pistol round, a tiny amount of powder creating a small amount of pressure that is expanding/dissipating as it travels down the relatively (for an AR) large bore. If you want to capture enough pressure to run the action you need the port to be close to the chamber. MAYBE you could get a long 20" barrel to work with a carbine length gas, and subs, but you'll probably find out the hard way why its just not done.

 

[wvfarrier]

Always go with a pistol length gas system for 300blk

 

[TonyTheTiger]

Always go with a pistol length gas system for 300blk

I wouldn't if I was shooting supersonic only..

 

[Haney]

Always go with a pistol length gas system for 300blk

Wrong .

 

[91Eunozs]

Always go with a pistol length gas system for 300blk

This.

After building literally dozens of 300 BLK uppers from 7.5” all the way out to 18”, with tens of thousands of rounds through them, I can honestly say the only ones I ever had problems with were the carbine-length gas barrels.

You can get them to run well with supers with careful tuning of your buffer system…usually with a huge gas port…but why limit yourself to just supersonic ammunition with 300BLK? It was literally designed for subsonic use.

A ton of fun suppressed too.

 

[wvfarrier]

Wrong .

Not hardly. That is specifically what I was told by AAC when I first began toying with 300blk.

 

[Haney]

Not hardly. That is specifically what I was told by AAC when I first began toying with 300blk.

Not hardly ? Double negative that literally means definitely or very . So I guess we agree ?

Shooting supers with a 16" barrel with carbine system . Ideal .