I have a S & W 500 magnum and using reloads of 300 gr. bullets, H110 powder and LR primers. The problem I'm having is every so often after firing the brass will not eject properly and I'm having to tap it out. They look as if something is burnt on the outside of the brass causing it not to eject. What might I be doing wrong. I clean the gun after every use but the problem seems to still happen. HELP.