I had loaded a 500 grain bullet with 70 grains of 777FFF and a 430 Grain with 65 grains of 777FFF. The 430 seats about an eighth of an inch deeper, so I used a little less power.
The 500 grains all ended up separating the cases, though the exact load fired in my springfield with no ill effects. The 430s didn't separate, but I did notice a stress ring forming on the case in the same location as the break in the other case.
I noticed that the breach can move back just a little, even with the hammer forward, and I wondered if this is causing the rear of the cartridge to move back wards and tear, or if it's something else.
Any rolling block experts? Also, the brass was R-P and has only been used 3 times max.
![Image](http://viciousbunny.net/images/rb/IMG_3180.jpg)