Light Primer Strike on Mossberg Shotgun, Photo
This actually happened with Mossberg shotgun which had the firing spring broken, but I have taken a photo to show you how light primer strike looks like:
Light Primer Strike on Shotgun
If you see such marks on extracted shells which failed to fire, you need to check and replace hammer spring to fix this problem.
Read also: Infographic: Remington 870 vs Mossberg 500
Vitaly, the first rule for such shells in not to touch them after ejection, slow detonation possible…
Stan, thanks for this advice, I have forgotten to write about that. I have taken those shell after some time, not immediately after extraction.