Originally Posted by
edp2k
That is a slam fire, where the bolt locks up and the FP has enough inertia to move forward and fire the primer.
In the cases where this happens typically commercial primers are being used, which are harder than mil primers.
A FP spring can mitigate this problem.
Militaries typically don't want to employ a FP spring as the fore/aft movement of a spring-less FP (imparted by the soldier walking with the gun)
"self cleans" the FP channel and helps prevent FPs rusting/crudding-up in place.
That is very different that the scenario shown in the OPs pics, which definitely fired out-of-battery, thus is not a slam fire.