Alright, today I went to try out my new 300 blackout pistol with some reloads I've made. The upper is 10.5" with omega rail. The loads are 15.8 gr of h110 behind a 150gr hornady fmj. They cycled great, but when shooting, I kept getting hit in the face with powder. Any suggestions as to why? Hornady says max load is 15.9 but people have said they've used 19 with no problem.