yeah nonlib hit it on the head higher preasure means a bigger bang and bigger bang means hotter and the lead melts and leaves little smears down the barrel so with a rifle round I would use a gas check. I cast as well and actually just casted 494 124 grain 9mm projectiles yesterday that im about to knock out of the panlube I had it in over night so me and the lady can go make sweet boom boom noise before nonliberals party tonight (you should come if you are free and get down with your bad self). I don't use gas checks in my 9mm ammo but after about 300 rounds shot thru it I have to do some heavy cleaning of the barrel to keep the accuracy of my loads up.
do you size them