Re: Slam fire and primers
Never had nor saw a slamfire; have a Garand, had an AR and an M1A, and nearly all my ammunition is handloads.
IMHO the key to avoiding slamfires is to use the ammunition and firearm the way they were designed.
The ammunition was designed to have the primer seated flush or below the level of the cartridge base. The firearm was designed to have all the rounds, even single ones, fed from the magazine.
Feeding the cartridge from the magazine incorporates the drag and deceleration produced by stripping and feeding the cartridge from the magazine. Hand chambering the round and allowing the bolt to fly into battery unhindered allows the bolt (and firing pin) to attain speeds that are significantly faster than is intended. This lends excess inertia to the firing pin, so it achieves primer impact with enough force to occasionally ignite one.
That's where the slamfires originate, and feeding from the magazine goes a long way toward preventing them.
Sometimes an M1 or M1A will double, firing a second round unintended. As long as the trigger group is essentially unmodified, this is not a slamfire or any other kind of mechanical malfunction.
It is an operator error. It is caused by babying the trigger. Again, the trigger is designed to be operated firmly and deliberately, pulling moderately quickly to the rear, all the way to the stop.
There exists a point along the path of the trigger where sear engagement is lost, but the trigger is not yet far enough to the rear to reengage the sear to the hammer hooks, entrapping it. The result is that the hammer rides the bolt, and will often fire again once the bolt has gone far enough into battery to allow the firing pin to clear the safety notch. The very presence of that safety notch is a tacit admission of the condition.
The design criteria is based upon having the operator pull the trigger firmly, smoothly, and without hesitation all the way back to the stop. Moving the trigger slowly rearward, 'hovering' near the release point, failing to follow through to a complete pull distance, will only aggravate the issue, and greatly increase the chances that doubling will occur.
I once experimented with deliberately inducing doubling. With a lot of (and I might add, nonproductive) practice, this condition can be induced with <span style="font-style: italic">some</span> repeatability. It serves no useful purpose, as the Garand, and M1A/M14 are all uncontrollable under conditions of full automatic fire. The additional round pretty near always goes somewhere around 5-10MOA high, depending on the shooter.
Greg
