i guess i am not following you are you trying to load a 125 grain subsonic load ? I dont think that you can load a bullet that light at subsonic speeds and i have tried in 4 different 300 blackout ars to shoot subsonic 220 grain loads without my suppressor and they would not cycle 3 16 inch barrels and 1 9.5 inch barrel so my experience and everyone i know that owns one couldnt get to cycle without a suppresor