ReluctantDecoy
NES Member
Keyholing is when the striker hits the primer and when retracting, drags along the striker face. This leaves a pronounced initial hit, then a slighter, but still very visible drag mark in the primer. I believe this is my Shield 9mm on the left and P365 on the right (been a while since I took the picture)er... OK, why does anyone care about this? Lots of guns do this without any problems at all.
Lots of micro 9's keyhole primers. However, it was a concern on the first batch of P365's because they keyholed very drastically and the metallurgy of the strikers wasn't up to snuff, leading to several reports of broken striker tips. Sig improved striker shape, slide striker hole (beveled it), and supposedly improved the hardening of the striker itself in the silent 2nd gen release. This picture is of my 2nd gen P365. So still happens, but supposedly less concern of breakage (supposedly).