I'm not saying that you are a novice or questioning your judgement, but consider why does a reduced carbine load of H110 cause pressures to skyrocket? Why does a normal 9mm bullet loaded to operate at say 28,000 cup pressure and the same load in an uncannalured case rise to 62,000cup when the bullet is pushed back into the case .030 deeper? (Straight out of the #10 Speer manual)

Below, excerpted from a 2010 CMPicon discussion of the subject, basically an autopsy of a busted carbine using slower powder.


"Other powders: Yeah, there are some that are a close match. The ones with a seemingly LOW pressure achieving STANDARD velocity are a problem in carbines. A low overall pressure achieving the standard velocity means a slow burning powder that extends the pressure curve father forward and creates a higher than normal port pressure. May not push on the bolt/cartridge case head hard, but it pushes on the gas piston harder than expected and slams the slide and bolt with more vigor than normal. If you can hear, you hear the wack/wack instead of a schuup/schuup sound. Using those slower powders may well not be an advantage if you understood what is going on inside the barrel and gas cylinder."

It's just information, may help, may not...