I am having trouble fully cycling subsonic loads. It will cycle supers just fine both suppressed and suppressed. When I use subsonic loads it will fire the round with the suppressor on and will eject the casing but will not pick up a new round. When I fire a single round the bolt does lock to the rear.

I am using factory 220 grain subsonic hornandy rounds and 208 grain remmington subsonic rounds.
I have a 8.5" barrel on a PSA upper and a DPMS lower.
-pistol length gas system
-YHM suppressor
-AAC FA bcg
-h2 Buffer and spring

Im not sure what is going wrong. Any help would be appreciated.

Who's barrel?  What size is your gas port?

Is the upper a purchase completed upper? You did not put in the barrel right? Its still a DI system?
Are you getting partial last round hold back or full hold back. Sometime with subs the bolt catch will hold BCG partial with part of the bold hanging out the mag follower. Try one round in a magazine and see if it catches at all during the cycle to determine what the travel is on the BCG. A partial hold can sometimes not pick up the next round.
What supers are you using?
Is your spring a standard spring?

I would try a carbine buffer. H2 is a little heavy for factory subs imo. The gas block maybe off a little but look at the buffer first for a simple fix. I think you are getting a partial LRHO which is causing issue with the next round and if you remove the weight from the buffer it will fix it. I had that issue with my piston blackout but I fixed it by running a carbine buffer and opening the gas port, but again that was with a piston system. BTW blackout is going to get you into reloading them its a fun round

Most likely  the buffer or the gas block.  I'd try firing it with a standard buffer/spring first since that's the easiest thing to change.  If it still doesn't work check your gas block alignment.  

really? mine cycles an H3 like a champ.



check the pipes man, check the pipes.

I am going to have to say it is in your gas system, needs some turning.

hee,hee, unless he got hold of a set of bushmaster gas rings.

its is a purchased upper, it was originally a 5.56 barrel on it that i had swapped for a 300. it is an AAC barrel. i put in my original buffer and it was having the same issues. And I have no idea what size the gas port is. it has a low profile set gas block on it. it seems to be that the gas block is aligned properly, although there is a few rings of carbon around it on the barrel. whats the best way to check alignment?

compressed air.

I do have an air compressor, how would that work?

I would check gas block alignment and try a standard buffer and spring.

blow air down the pipe and move the block unitl you hit the sweet spot. check for any obstructions first. if you can measure the port when you are checking it that will help.

so the gas block was good with the air through it. I removed the weight completely from my buffer and that seemed to solve the issue. it is now cycling subs through the suppressor fine. however it is not locking to the rear with a single round magazine. it still fires supers just fine both with suppressor and without, and locks to the rear with a single round magazine.

if everything checked out fine your port is undersize.

Put your finger in the chamber to seal it up and your lips on the barrel.....then blow....air will easily go out the gas port and block if it's aligned.. If not you'll turn red.. It sounds stupid but it works. Air compressor works too. If that's not it then your port is to small. Measure it.

Depends on your factory ammo. My reloads work great

then i guess your port is undersize too...

Drilled it out so it would run

AAC barrel, so I doubt it is the gas port.  What weight subsonics are you using?

never seen a 8.5" AAC pipe but it is the internet so...



im sticking with the port.