I have an old Remington Model 742 semi auto rifle. I've noticed that when chambering a cartridge, the firing pin is leaving a slight dimple on the center of the cartridge even when it is not fired. If fired, the next cartridge loaded has the same dimple. I keep expecting it to fire upon chambering a cartridge or to double fire. Does anyone have any ideas on what's causing this or how to repair it? Any suggestions would be greatly appreciated.