hawkeye40

I guess you are right, I just like to do the amateur gunsmith bit and understand where the problem is first.

Yse, the mark on the primer is light. It could be a weak spring. I have removed the pin and it was relatively clean. The cartridge was an Express clay cartridge, it happened more than once.

Could anyone advise what the firing pin extrusion should be for a 12 bore. I have a winchester 101 and suspect the misfire problem is due to lack of pin protrusion. the pin does look a bit pitted. Any help appreciated.