Sometimes when what I'm seeing posted on these forums doesn't make sense to me, I have to try it myself as a kind of sanity check.



When I fired the normal case, I pressed my rifle's bare muzzle (no flash hider) against a folded towed and watched for any bolt carrier movement. Nothing, zero, nada - even with the magnum-strength CCI 450. Considering that the carrier would have to retract at least 1/8" before the bolt even started to rotate, it seems highly unlikely a primer would produce enough volume of gas to cause unlocking. There must be another explanation for the phenomena described in earlier posts on this thread.

My guess is that the extreme primer protrusion Curt described was from a loose primer (undersize cap or expanded pocket) that moved back during ejection - a result not of pressure but simply inertia. That's something I have seen, especially with military cases where a trace of the annular crimp remains to catch the front edge of the primer cup and keep it from falling out completely. Primers found in this condition can often be pushed back into the pocket with little effort, demonstrating that they are not tightly fitted.