Ah, cool. I figured there was a pretty big pressure delta between low base and HV 3". I just have no idea how much, is it an order of magnitude?
Yeah, I haven't pulled my RPK apart that much (it amuses people the times it has been broken down... well OK, I also clean it when I feel the OCD coming on), I consider it an art piece and so haven't even taken it to the range or owned ammo for it.
I wondered about pressure variation. So if you widened the opening this would help a bit but in the end you'd end with people swapping out the upper gas system for some freakish big pipe solution (a