New to board, hope I can get some help with a misfire problem. My Mini 30 misfires using russian or other east euro rounds. pin dimples the primer. About every 3rd or 5th round sometimes worse. It will misfire using Winchester on rarer occasion, 1 in 30 or 40 or so. I have approx 500 rds thru it now. Bought used and unsure of any history. Thanks in advance for any assist.