The Firing Line Forums - View Single Post - Primer deformation... What am I seeing here?

FrankenMauser · July 14, 2012, 11:20 PM

What you're describing is generally referred to as "cratering" (as mentioned by wncchester). The actual cause depends on the firearm the cases were fired in.
Cratering can be cause by a sloppy fit of the firing pin to firing pin channel, or by excessive pressures.

With 5.7x28mm, things are a little more tricky. Because the 5-7 brass stretches and pushes the shoulder forward when fired, it can hide other pressure signs. Since the 5-7 runs at rather high pressure, to begin with, you don't have much leeway before serious pressure signs suddenly emerge. (case rupture, blown primers, loose primer pockets, etc.)

Keep an eye on it.

July 14, 2012, 11:20 PM	#7
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,424	What you're describing is generally referred to as "cratering" (as mentioned by wncchester). The actual cause depends on the firearm the cases were fired in. Cratering can be cause by a sloppy fit of the firing pin to firing pin channel, or by excessive pressures. With 5.7x28mm, things are a little more tricky. Because the 5-7 brass stretches and pushes the shoulder forward when fired, it can hide other pressure signs. Since the 5-7 runs at rather high pressure, to begin with, you don't have much leeway before serious pressure signs suddenly emerge. (case rupture, blown primers, loose primer pockets, etc.) Keep an eye on it. __________________ Don't even try it. It's even worse than the internet would lead you to believe.