Ok,
It's been a long time since I really reviewed 300 Blackout info(it was actually 300 Whisper back then), but I remember some discussion on the pistol length gas system being more reliable for it?
I am wondering in the 14" and up barrels does the pistol length gas system have any problems with supersonic loads?  Wondering if long term it beats the buffers to death or any other problems.
Anybody with some trigger time in their 14" or 16" 300 BAs I'd like to know opinions and input on the pistol length gas system vs carbine.

Thanks for any input here. I had a carbine length gas system on my original 300 Whisper, but considering the pistol length on my 300 BA upper build.
SS33

I have blackouts in 8.5, 9 and 16 in barrels. One of the 16s has carbine gas (YHM) and the other has pistol (KAK). I always shoot with a suppressor. The carbine length was my 1st 16 and it needed just a little tweaking of loads to get it working with the same ammo as the 8-9s. The KAK was giving me all kinds of fits. It would only feed Remington factory 220s reliably. On anything else it caught the round at the shoulder, including factory Hornady 10s. I finally found that the barrel had an extra large gas port and I bought an adjustable gas block for it and now it seems to be working right (I still need some more rounds through it). This one is the only one I have that need an adjustable gas block.

I just finished a 14.5"/pistol gas upper.

Only 30 rds fired, and aprox 20 of those were single feed from mag, and the bolt locked back every time.

Loads were Remington 220gr OTM Subs.

I haven't shot supersonic, but the subs shoot........wonderful!

May be the nicest shooting rifle I ever fired. Everytime it fired, I was surprised it cycled. Its VERY smooth, ZERO recoil, just a joy to shoot. Brass just kinda pops out at 3 o clock.

My 5.56 upper shoots fantastic, but with the muzzle blast, its just not the same. After the 1st shot out of the blackout, for 1/2 a second I thought....shoot up the 5.56/.223 ammo, sell the 5.56 upper and start chopping brass...LOL

Edit...

Everything I read, for the most part, said 16" barrel, pistol or carbine gas system works, but anything UNDER 16" will need a pistol system.

I used a 14.5", pistol gas, Ballistic Advantage, 1x7 twist barrel. I built it for subs, so I wanted the faster twist. I think I read it has a .076 gas port, could be wrong, but its very close. Non-adjustable gas block. Carbine spring, H buffer.

I went and found the post that helped me out.

Read what "TurnTwo" has to say.

Pistol length functions better with subs

I have a 14.5 with a carbine gas and it functions full power ammo fine. I don't have a suppressor and have never tried subs in it. I know it would not play nice with subs.