Baribal, my 30-30 always has protruding primers due to the "normal" low pressure of this cartridge at 38,000 cup or 42,000 psi and there is no gas leakage around the primer.
At low chamber pressures the primer is the first thing to move and contact the bolt face, and this is called headspacing on the primer. If the primer cup is too hard or the primer pocket is oversized it will not seal the primer pocket and you can have gas leakage around the primer. The OPs primer cup ruptured at the edge of the primer cup radius, this is primer failure and has nothing to do with headspace. A Enfield rifle at maximum military headspace can have as much as .017 head clearance or excess headspace and the primers do not leak.
I found this AR15 5.56 case below at the range when picking up my own .223/5.56 cases, when I first saw it I thought someone modified their cases to use large rifle primers. When I removed the primer from this case it looked like a mushroom, in simple terms this primer was soft enough to "flow" to its mushroom shape and not rupture at the edges. This over zealous reloader not only removed the military primer crimp, but he removed over 25% of the primer pocket and the primer did not rupture when fired.
On a over gassed AR15 rifle there is still pressure in the barrel when the bolt is moving to the rear. This can cause the primer to pop out of the primer pocket like a champagne cork and fall into the trigger group. When this happens there is no damage to the bolt face from high pressure gases because the primer was soft and sealed the primer pocket. The primer is the piston and the primer pocket is the cylinder and as long as the piston seals the cylinder, you will not have blowby leakage. This is just one reason primers are crimped on military cartridges and hold them in place.
Last edited:
