AL45,
The accepted probable cause of 'slam-fires' is in the design of bolts with 'free-floating' and spring supported firing pins. Simply, the bolt flies forward, the round is chambered and comes into battery, the locking lug/s connect and lock... the inertia of the moving firing pin carries it (the firing pin) forward into the primer! I have never encountered a 'slam-fire' but often I will see very small and light dimples on primers of rounds that have been chambered, M1A/M14 type weapons most often.
This does not preclude other actions or failures that may also cause a 'slam-fire'. A 'high' seated primer could be a culprit in this. Personally, I haven't knowingly seated primers 'high'. I did have a .22RF rifle get a small sliver of bullet lead wedged in with the firing pin (more of a bar running the top length of the bolt) and had repeat firings! Pull the trigger once and get 3 or 4 rapid shots. Very unnerving. So, this could be described sort of as a 'slam-fire', stretching my definition a bit.
I have seen entries by a contributor who has studied 'slam-fires' and find his conclusions very compelling and well researched. Always something to keep in mind.
Always error on the side of caution,
OSOK
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