A key contributing factor in slam fires is bolt velocity at time of battery. The system is designed to feed new arsenal/factory ammunition from the magazine, and that process retards bolt velocity to a point where the floating firing pin should lack sufficient velocity to initiate the primer.
The possibility of a primer standing proud is a reason why handloaded ammunition MUST be screened for this condition that is part of the QC process for arsenal/factory ammunition.
The intended feeding process can be defeated by several conditions.
The first is caused by circumventing the intended magazine feeding process. This allows the bolt to slam into battery without any of the intended retardation from picking up and feeding the round. Because some GI's will always find the wrong way to do things, the military primer's harder cup was instituted in an effort to reduce damage and injury from improper feeding.
Another is from improper cleaning of the bolt assembly. This must be done somewhat frequently in order to remove the crud from the pin and channel. This crud can immobilize the firing pin, and if the resulting orientation involves pin protrusion, the primer can be initiated on an infrequent basis. Dry firing the rifle several times before commencing firing can improve on this situation until a proper bolt cleaning can be performed.
Another cause is chamber crud, which can result in a jammed round and an out of battery discharge.
This information stems from my training at MCRD Parris Island, and ITR Camp Geiger in 1966 where both the M-14 (MCRD) and Garand (ITR) were issued.
Greg
The possibility of a primer standing proud is a reason why handloaded ammunition MUST be screened for this condition that is part of the QC process for arsenal/factory ammunition.
The intended feeding process can be defeated by several conditions.
The first is caused by circumventing the intended magazine feeding process. This allows the bolt to slam into battery without any of the intended retardation from picking up and feeding the round. Because some GI's will always find the wrong way to do things, the military primer's harder cup was instituted in an effort to reduce damage and injury from improper feeding.
Another is from improper cleaning of the bolt assembly. This must be done somewhat frequently in order to remove the crud from the pin and channel. This crud can immobilize the firing pin, and if the resulting orientation involves pin protrusion, the primer can be initiated on an infrequent basis. Dry firing the rifle several times before commencing firing can improve on this situation until a proper bolt cleaning can be performed.
Another cause is chamber crud, which can result in a jammed round and an out of battery discharge.
This information stems from my training at MCRD Parris Island, and ITR Camp Geiger in 1966 where both the M-14 (MCRD) and Garand (ITR) were issued.
Greg
