Bart Bobbitt’s opinions date from 1994. This dates from the era when “only high primers” caused slamfires. He was trying to establish a mechanical cause.
So, I'm convinced that virtually all slam-fires are caused by insufficient sear and hammer hook engagement.
We all can agree that mechanical malfunctions, such as the hammer following, can cause slamfires. Everyone who competed with an M1a saw “doubling”. A poor trigger job caused the hammer to follow and the shooters rifle doubled. However every double I saw and heard, when the shooter tried to shoot another ten rounds rapid, the rifle would double again. Then we would kick him off the line. Once a trigger mechanism is out of mechanical order it stays out of order.
Some people milk the trigger mechanism, and with a sand bag rest, get doubling. That happens and if the hammer follows, could result in an out of battery slamfire. Still, with enough reports on the web, it is being accepted that sensitive primers will initiate a slamfire. Something that was not acknowledged back in 1994.
All of which means these slam fires happened because something made
the firing pin drive hard into the chambered round's primer.
And his conclusion is totally 100% wrong. I have picked up my slamfire round from an AR, and that of a friend, and the primers looked totally normal. I know for a fact that my safety was on. I know for a fact that my friend’s rifle functioned for the rest of the day without any trigger malfunctions. Both of our AR trigger mechanisms are still functioning normally years and replacement barrels after our slamfires.
I don’t know why slamfire primers look normal. Maybe a high speed camera would show why.
I am still using the same trigger mechanism that was in my second slamfire rifle. The trigger mechanism is still working fine. And I am not ever going to use Federal primers in a Garand ever again.
Bart Bobbitt’s assigned cause to slamfires was mechanical only, totally ignoring primer sensitivity as a cause. This was part of the delusional thinking back in those days: a primer was a primer was a primer. They were all round and shiny and all the same. To suggest that one primer type was more sensitive than others, that primers within a lot varied in sensitivity, or that a Garand's or M1a’s free floating firing pin had the inertial energy to set off a sensitive primer, why that was absolute blasphemy to the shooting community.
Read the posts on the Rem M700 trigger and the CNBC special. You got the same sort of emotional denialism if you suggested that sensitive primers could cause slamfires.
Bart Bobbitt’s post is simply a blast from the past.
It is all a matter of risk. How much risk are you willing to accept?. I know of people who shot tens of thousands of Federal primers in Garands and M1a's.
I also know one gentleman, Joe L, who had his Garand barreled with a Wilson match barrel. We talked about his incident in the pits. He wanted to compete in the Garand Match with a good barrel. He full length sized once fired brass in a standard sizing die, he did not use a case gage to measure how much he was pushing his shoulder back, and he primed his cases with Federal primers. I don't think he fired 20 rounds before his rifle slamfired out of battery and blew the back of his receiver off. His comment to me was "people ought to know how dangerous these rifles are to reload for."
My second slamfire was with a Garand fresh from the gunsmith. It had a new heavy Barnett barrel and was totally matched out. I had fired enough shots to center the post, so I had a mechanical zero on the rear sight when the rifle was shooting to the center of the target. Then I inserted a clip of eight rounds to verify function from the magazine. All of these rounds had Federal primers, hand seated in reamed primer pockets. The rifle slamfired out of battery somewhere in the clip, blowing off the back of the receiver. I guess I had less than 30 rounds through the rifle. Maybe 20. It was not much.
At least the stock, handguards, trigger guard, gas cylinder, operating rod, were salvageable.
Here is a slamfire that helps put the lie to Bart Bobbit's post.
Tavor 21 Slamfire video on youtube.
Notice how many rounds the guy fires. If he had a mechanical problem he would have recurring slamfires, but he did not. When you see the slamfire, notice that the finger is not on the trigger. He was running Federal American Eagle (federal primers) and Winchester ammo. Winchester redesigned their primers in 1999 to make them more sensitive.
This weapon slamfired in battery. The risk with Garands and M1a’s, is that they have often slamfired out of battery.