please forgive my ignorance as I am new to forums and have never asked a question on one before. I have been reloading now for the better part of 15 years but my experience has been primarily in metallics. I have been casting now for a little over 2 years and just recently started to cast for my 300 blackout. I am using primarily wheel weight lead and water quenching the bullets for hardness. I am using the Lee 312-155 mold and sizing them down to .309 using a lee sizer die. I am then lubing them with Lee liquid alox and gas checking them with a copper check. I am fairly confident (emphasis on fairly) that the bullets are working decent as I'm keeping a 4" group at 150 yards. However the issue I am having is I can only get about 1-3 30 round magazines out before the bolt is so gummed up it seizes forward due to either lead or carbon powder in the BCG and star chamber.
I am using Lit'l gun powder at 15 grains. Again if this were metallics I wouldn't be having the issue as I have been able to fire well over a 1000 rounds of FMJ's with the same powder through the same gun with no issue.
So I guess my question is am I doing something wrong? Or has anyone else had the same issue? Is there a fix to this or am I just kind of stuck cleaning a BCG and chamber after every mag?
Any help would be greatly apreciated thank you in advance for any advise or imput.