I had a problem with my Garand when I went to a too strong recoil spring. Just got double taps.
Problem went away when I went back to a GI spec spring.
Not always a primer problem though sure can be.
I agree that primer initiated slamfires are a subset of all causes. However it is the one with the least recognition and most denial.
Many folks just believe that a primer is a primer: primers are all round and shiny and all the same. You will see posts by guys who proclaim with revolutionary fervor that there is no such thing as a milspec (less sensitive) primer.
Mechanisms with free floating firing pins are particularly prone to slamfiring with sensitive primers. Your rifle probably slamfired because the forward speed of the firing pin was increased by the strong recoil spring. Just that little additional speed was enough to overcome the ignition threshold when the firing pin bounced off the primer.
There are some reports of slamfires in AR’s that have the operating rod conversion. My guess is that the additional weight of the carrier increased forward velocity during cam down.
Incidentally, if you look at the “Black Rifle: An M16 Retrospective:
http://www.amazon.com/Black-Rifle-M16-Retrospective/dp/0947898867 there is half a chapter on the early slamfires the Army/Marines had with the M16, and what they did to reduce them.
MMMM slamfires.....
legal machine guns
Illegal machine guns. Search and you will find a guy who leant an AR to a friend, the AR slamfired at the range, and the original owner is now in jail for processing a machine gun. Search some more and you will find that the BATF took a FAL owner to court for owning a “machine gun”. According to the FAL owners statement, a spiteful person sic'd the BATF after him. The BATF then found commercial ammo with sensitive primers (it was Winchester) and got his rifle to slamfire. The owner had to go to court.
Maybe the moral of the story is, follow safe reloading practices or the BATF will ensure you have unsafe sex in prison!.