Slamfires are very real phenomena with semiautomatic mechanisms. People attribute slamfires to mechanical things, like stuck firing pins, grease in the firing pin hole, hammer following the bolt, all of which will cause a slamfire, but when it comes to primer sensitivity, folks just will not acknowledge this as a factor, instead you get absolute denial.
Imagine this, you have a primer and a firing pin with sufficient energy to ignite the primer. What happens when the firing pin hits the primer?; the primer goes off. Imagine you have a free floating firing pin attached to a rapidly moving bolt carrier and a round is being fed into the chamber. And before the trigger is pulled the firing pin hits the primer with sufficient energy to ignite the primer. What happens?; the primer goes off. If the primer goes off before the bolt is in battery you have an “out of battery” incident. That is likely to be a destructive event.
The SKS with a free floating firing pin is particularly susceptible to slamfires. So is the M1 Garand and the M14 mechanism. The original M16 configuration had slamfires in service so the military redesigned the firing pin to make it lighter. If you notice the FN/FAL firing pin is spring loaded, so are Russian SKS designs, and so are the AR10 designs. All needed to keep a sensitive primer going off when hit by a rapidly moving firing pin.
I used sheaves of WSR primers when they were nickel plated. They were excellent But around 1999, Winchester changed their primer by eliminating the “nickel” finish to a “brass” finish. I called Winchester to find out what this change has done to primer sensititivity. Per telephone conversation with Mr. Chris Huseman at Winchester Group, Olin Corporation 618-258-3565, the old WLR primer had a zinc plating on the cup. Mr. Huseman said the material was zinc, (even though I thought it was nickel). Anyway, Winchester removed that plating, perhaps with other changes, to make their primers more sensitive. The product change was specifically targeted to “combat light firing pin hits and off center strikes.” Which is of course is fine for bolt guns, revolvers, or monkeyed with auto pistols, but is something you do not need in a military action or a gas gun. The result of making the cups thinner is pierced primers and the occasional slamfire.
I had one slamfire in the AR, I dropped a round in the chamber, during the standing stage, and released the bolt. The round took a divot of dirt out in front of the firing line. It was a new brass WSR primer in the case. The next shooter on my point did the same thing, dropped a .223 round in with a Fed Match primer and also got a slamfire. I seat my rifle primers by hand with a Lee Primer and inspect each primer. I did not have a high primer.
Something to remember about AR’s, if you can, single load through the magazine. If you drop a round in the chamber, hold the bolt back using the charging rod, trip the bolt release, lower the bolt about half way, then release the charging rod. Finally bump the forward assist. It is always good practice to bump the forward assist on the first round, mag fed or port fed.
CCI is the only manufacturer who claims to make a “Mil Spec’ primer. When talked with CCI, I was told that these primers are less sensitive than commercial and are magnum primers. I have used CCI#41 in my match AR’s for years now, shot my absolute best long range scores at Camp Perry with them (didn’t clean the target but came close). I am surprised that someone else has had a problem with them.
Because primer sensitivity equipment is not available (like chronographs), people can’t test primer lots and see the varying levels of energy it takes to ignite primers. They also don’t know the kinetic energy of the free floating firing pin. The “conventional wisdom” is that all primers are the same and therefore slamfires are only due to high primers. This assumption is false, but I don’t have the data to prove it. And neither do the people who insist that primers are all the same, or that primers don’t vary from lot to lot, or even from primer to primer.
I do believe that a high primer will cause a slamfire. But an overly sensitive primer will occasionally ignite even if properly seated. It may be one in 50,000, it might be one in 1,000,000. But it has happened, does happen, will happen.
Imagine this, you have a primer and a firing pin with sufficient energy to ignite the primer. What happens when the firing pin hits the primer?; the primer goes off. Imagine you have a free floating firing pin attached to a rapidly moving bolt carrier and a round is being fed into the chamber. And before the trigger is pulled the firing pin hits the primer with sufficient energy to ignite the primer. What happens?; the primer goes off. If the primer goes off before the bolt is in battery you have an “out of battery” incident. That is likely to be a destructive event.
The SKS with a free floating firing pin is particularly susceptible to slamfires. So is the M1 Garand and the M14 mechanism. The original M16 configuration had slamfires in service so the military redesigned the firing pin to make it lighter. If you notice the FN/FAL firing pin is spring loaded, so are Russian SKS designs, and so are the AR10 designs. All needed to keep a sensitive primer going off when hit by a rapidly moving firing pin.
I used sheaves of WSR primers when they were nickel plated. They were excellent But around 1999, Winchester changed their primer by eliminating the “nickel” finish to a “brass” finish. I called Winchester to find out what this change has done to primer sensititivity. Per telephone conversation with Mr. Chris Huseman at Winchester Group, Olin Corporation 618-258-3565, the old WLR primer had a zinc plating on the cup. Mr. Huseman said the material was zinc, (even though I thought it was nickel). Anyway, Winchester removed that plating, perhaps with other changes, to make their primers more sensitive. The product change was specifically targeted to “combat light firing pin hits and off center strikes.” Which is of course is fine for bolt guns, revolvers, or monkeyed with auto pistols, but is something you do not need in a military action or a gas gun. The result of making the cups thinner is pierced primers and the occasional slamfire.
I had one slamfire in the AR, I dropped a round in the chamber, during the standing stage, and released the bolt. The round took a divot of dirt out in front of the firing line. It was a new brass WSR primer in the case. The next shooter on my point did the same thing, dropped a .223 round in with a Fed Match primer and also got a slamfire. I seat my rifle primers by hand with a Lee Primer and inspect each primer. I did not have a high primer.
Something to remember about AR’s, if you can, single load through the magazine. If you drop a round in the chamber, hold the bolt back using the charging rod, trip the bolt release, lower the bolt about half way, then release the charging rod. Finally bump the forward assist. It is always good practice to bump the forward assist on the first round, mag fed or port fed.
CCI is the only manufacturer who claims to make a “Mil Spec’ primer. When talked with CCI, I was told that these primers are less sensitive than commercial and are magnum primers. I have used CCI#41 in my match AR’s for years now, shot my absolute best long range scores at Camp Perry with them (didn’t clean the target but came close). I am surprised that someone else has had a problem with them.
Because primer sensitivity equipment is not available (like chronographs), people can’t test primer lots and see the varying levels of energy it takes to ignite primers. They also don’t know the kinetic energy of the free floating firing pin. The “conventional wisdom” is that all primers are the same and therefore slamfires are only due to high primers. This assumption is false, but I don’t have the data to prove it. And neither do the people who insist that primers are all the same, or that primers don’t vary from lot to lot, or even from primer to primer.
I do believe that a high primer will cause a slamfire. But an overly sensitive primer will occasionally ignite even if properly seated. It may be one in 50,000, it might be one in 1,000,000. But it has happened, does happen, will happen.
