It looks to me like the firing pin has a broken tip and might be sharp, and if the primer unseats (as they sometimes do, especially if the primer pocket is worn from too many reloads) it could be spitting a chunk off the primer before reseating itsself. When you punch out the primers to reload, do they come out too easily? or do you have to use normal force to get them out?
try some factory rounds, see if they do it too.... then you will know if it is a problem with your gun
Muzza