Range time today

I took my 10.5" blackout to the range today with 110 gr vmax on top of 20.2 grs h110. Four shots without the suppressor followed by 10 with it. The suppressor moved the poi 2" left and 2"down at 50 yards. This is the first time I've shot an ar with a suppressor. Boy does that make them dirty, the remaining rounds in the magazine were filthy!
Before I quit I fed it a subsonic round. For some reason that locked it up, the empty is still in the chamber with the bolt closed. I'll deal with that later.

Probably undergassed for the subs and suppressor. I really enjoyed mine but I was teaching my grandson on ARs and I just didn't feel comfortable with it any longer. Too easy to mix the two. Sold it and a few thousand rounds of the Aussie rounds at 41 cents per round which is what I paid for them. Believe when I sold it to a friend basic rounds were about 1.50 per or so. But they do blow the crap out of stuff. Believe my was 10.5".

Since it's wearing a brace that for some reason is easier to shove up than pull back I didn't morter it. When I got to it this morning a little tap on the charging handle with a rubber mallet opened it up just fine. I doubt I'll put the suppressor on it or shoot subs in it again. Quiet is for the bolt action, and since this is a bump in the night gun it'll be fed a diet of 110-135 gr ammo.
Anyway, it's all cleaned and oiled and the suppressor is taking a long drink of Ed's Red.

What suppressor & attachment method?

Sounds like it’s under gassed & part of the problem could be the suppressor

The Rattler has an adjustable gas block, 2 settings, 1 for supers and 1 for subs. Have not shot it yet & still making changes

The 10.5” 300 black AR15 runs great on both supers and subs, put the Deadair K on and supers are fine but it does what you describe for subsonic ammo

Have never cleaned a can or thought they got dirty, but I am lazy

I went and got Magpul’s 300 blackout magazines and different magazine rubber bands on Amazon that say 300 blackout & super or subsonic