I reloaded some 77 grain HPBT match bullets for my 223 (R-15 Rem) using MR2000 powder to see if my 1:9 twist would stabilize them. (It does). My stoutest load was 24.9 grains which is under listed max in the Alliant reloading info by a bit. These were loaded to max Mag length. There was still room for powder in the case.
I ran the loads up from somewhat lower, but even at 24.9 grains, I didnt have any signs of pressure. No flatted primers anyway. I did notice that it "seemed" that the buffer spring was louder than usual when I fired.
Anyway, the question I have is, how do I tell if a load is too hot for a semi-auto? Can I rely on pressure signs on the primer?... or if I get primers flattening have I already exceeded a safe pressure for my rifle. I not only want to prevent being over SAAMI pressures, but I want to not wear out my rifle prematurely for a few lousy FPS. Man, those 77 grains bullets shoot nice. I'll have to look and see if Sierra makes a gameking in a 77 grain. That would be a coyotes nightmare at 2700 FPS.
So what is the limitation to max pressure in gas guns versus bolt guns?