Thread: What in the world?

Originally Posted by Gkp

My guess with the dents is that upon firing when the head seperates the rest of case fires foward in the chamber rapidly witch compresses the case much like what happens when you bump the shoulder back to far when resizing.
Only a theory of course

Close Gyp,
What actually happens is that the force of the firing pin hitting the primer and the primer going of shunts the whole case to the front of the chamber. You can often see this with sub loads where the primer is protruding from the back of the case due to the low pressure. As pressure builds the front of the case grips the chamber walls and the case head is forced back over the primer to contact the bolt face. This is the point where the case may separate. If it does then the gas can flow forward until it gets to the shoulder that is still pressed tight into the chamber. The dents we see form at this point. Dents like that can also form with very low pressure loads. And it all happens in microseconds!
Regards Grandpamac.

Originally Posted by grandpamac

Close Gyp,
What actually happens is that the force of the firing pin hitting the primer and the primer going of shunts the whole case to the front of the chamber. You can often see this with sub loads where the primer is protruding from the back of the case due to the low pressure. As pressure builds the front of the case grips the chamber walls and the case head is forced back over the primer to contact the bolt face. This is the point where the case may separate. If it does then the gas can flow forward until it gets to the shoulder that is still pressed tight into the chamber. The dents we see form at this point. Dents like that can also form with very low pressure loads. And it all happens in microseconds!
Regards Grandpamac.

Grandpamac, in the case of a bolt with a plunger ejector, would it not be the plunger holding the case forward in the chamber and not the firing pin driving it forward ??