Originally Posted by larrywillis;838549When you see that 99[B
.[/B]9% of all case head separations are at the rear of the case . . . . . it's obvious.
That's not the reason.
It's partially the thinner case body wall at the shoulder and thicker case wall at the head that causes it as the front part of the case is pushed hard against the chamber wall long before the back part is. It's the back part that does most of the stretching.
The other part is the pressure ring area is where maximum work hardening of the case is at from enlarging when fired to reducing when sized down. The head and back 1/8th inch of the case changes diameters very little. It starts 2/10ths inch in front of it is. That weakens the case body at that point.
Rarely, if ever is there such a thing as "shoulder" separation. The case head breaks off from all the elasticity being removed from the brass at the pressure ring.