Has anyone ever experienced one?And while we are on the subject what is your load.

I like 46gr IMR4895,WLR,150gr Core Locks in mine.

I have put a lot of rounds downrange through M1 Garands, M14's & M1A's but not too much experience with the AR's and none w/AK's, so following refers to the M1 types.

Other than a dirty chamber, a broken firing pin or a pin that is no longer free floating for whatever reason, IMHO, ammo is probably the number one cause of slam fires. Anything that can cause the round to "stop short" of full chambering can result in the firing pin hitting the primer with sufficient force to set it off. If this occurs before the bolt is in battery, it can be disastrous!

Soft primers can result in slam fire, as can a high primer. The CCI #34 military primer has a hard cup to duplicate GI ammo, most of which is loaded with a hard primer. Handloaders must be aware of two other factors in order to avoid slam fires.

First, make it a practice to run your thumb over the primer as each round is removed from the press to be sure that the primer is fully seated.

Secondly, each cartridge must be sized sufficiently to fit chamber giving proper headspace clearance. I would not load for any "gas gun" without using a cartridge case gauge. Best practice is to run each case through the case gauge at the time the loaded round comes off the press. At the very least, spot check every few rounds in a given lot of reloads (for this to be acceptable, one must keep all brass in lots that have been fired the same number of times).

To illustrate the importance of the above statement, had a friend who is a very experienced highpower competitor and reloader who wrecked his match grade M1 Garand using the same handloads he has used for years when the rifle slam fired out of battery. Bent his op-rod, blew extractor/ejector out of bolt and rounded the receiver locking lug recess about 1/8" showing the bolt lug had barely entered the recess and was not in battery at the time the slamfire occured. He received a cut on the forehead and had a little problem with his trigger control for a while afterwards. Fortunately, the rifle, and his shooting ability have since been repaired.

Upon examination of the remaining lot of ammo, we found that the rounds did not have sufficient headspace (clearance) in his snug chamber. He had loaded this batch of ammo using the same die setting as always and other lots measured OK. The problem stemmed from the fact that this particular lot of brass had been fired quite a few times and had work hardened and his dies had been set to give proper headspace with once fired brass. The harder brass springs back more than softer brass after sizing.

Hopefully, this information may help someone else avoid this pitfall.

Your load will closely duplicate the M2 Ball load originally used in the M1.

Regards,
hm__________________

quote:

The problem stemmed from the fact that this particular lot of brass had been fired quite a few times and had work hardened and his dies had been set to give proper headspace with once fired brass. The harder brass springs back more than softer brass after sizing.

Hm, I'm sorry, but I just don't understand the above statements. If the brass 'springs back" after sizing, how in heavens name will you know it without hand chambering every round? Something that I never do!
Peter.

quote:

Hm, I'm sorry, but I just don't understand the above statements. If the brass 'springs back" after sizing, how in heavens name will you know it without hand chambering every round? Something that I never do!
Peter.

The more times a case has been fired/resized, the harder it becomes, much the same as a piece of wire will get hard and break after being bent back and forth many times. The harder the case becomes, the more it will spring back after being sized.

When setting up my sizing die the first time for a given rifle, I measure a once-fired (soft) case from that rifle and adjust the die to produce a sized case which measures .001-.002" smaller than the once fired case (for bolt guns) and if loading for a gas gun .002-.003" smaller. The case is measured using an RCBS case micrometer (or similar tool which measures case head to shoulder length).

I keep all my gas gun brass in lots which have been fired the same number of times and run every fifth round or so through a headspace gauge as they come off the press to assure sufficient headspace as a safety precaution.

Regards,
hm

Back to the original question...In over 40 years of active shooting, competetively, military, and law enforcement much of it done with the exception of military, with handloads, I've never seen a slam fire. Were talking hundreds of thousands of rounds fired and witnessed.

IF such a thing occurs, I would put it to a high primer or protruding firing pin either broken or jammed due to debris making the firing pin extending past the bolt face.

make sure your primers are seated all the way .a high primer will cause it to double.

The best way to check reloaded ammo for an M-1 is with a case length gage. You drop the loaded round into this gage, and if it goes flush, you are good to go. If not, check and see why. Most of the ones that don't "flush" have burrs on the case head from extraction. I sand them off with my dremel tool.

Although I have never had a problem, we had a spate of blow ups at our range a couple of years ago. It was enough for me to follow the procedures mentioned above and full length resize, use M34 primers, check primers and use my case gage. A blown M1 or M14 is a sorry sight. Kudude

Free floating firing pins like on the AK's will slam fire every time with standard primers. I have repaired many by springing the pins so guys could shoot handloads. All you had to do was drop a round in the chamber and release the bolt. They would fire every time. Military primers would not go off.
A case that is oversize and doesn't enter the chamber all the way is dangerous with a floating pin.

Thanks for the good replies.That is what I wanted.

check the bolt make shure the fp is not stuck out the best thing u can do is disasemble the bolt and clean it thouroly. sometimes gunk builds up in the firing pin slot. the easyest way ive found is use gunscrubber ( or equinelent) spray it in the hole goos use a lond q tip to scrub the inside snd spray hard again. this is the best way ive found to do the bolt on my m-1 match rifle ditto on checking the primer seating brian

The general public may not hear about slamfires, but they do happen. Because it is not considered an intelligent thing to blow up a rifle, people who have blow up a rifle are a bit reluctant to talk about their experiences. Recently I have had discussions with two experienced shooters who both had out of battery incidents with Federal primers, one with a 308 M1 Garand, and the other with a M1A. They would have never mentioned it if I had not brought up the topic. The gunsmith who installs match barrels for Champion Choice told me he receives two to three blown up rifles each year, mostly Garands or M1A’s, and the blow-ups are all with reloaded ammunition. He receives any number of calls from people who have functioning problems with their newly re-barreled semi-automatic. Always the problem is traced to reloaded ammunition which had been fired in a different rifle, usually with a military chamber. The rounds are inevitably too fat or too long because the standard sizing die was not able to reduce the cartridge dimensions to fit within a commercial chamber. Given the condition of a slightly oversized case, a supported but sensitive primer, and the free floating firing pin found in most semi-automatic mechanisms, an out of battery condition can occur. I believe to reduce the potential of a slam-fire, first full length resize with small base dies, size to SAAMI minimum, and prime with “Mil Spec†primers.


All that it is required for a slamfire is a free floating firing pin with sufficient energy to ignite a primer.

Primers have "none fire" and "all fire" energy tolerances. In the first fielding of the M16 they found that the firing pin energy of the M16 was above the "none fire" criteria of commercial primers. They were having out of battery slamfires. The military had to go back and redesign the firing pin (to make it lighter) because the ammunition maker refused to redesign the primer.

The M1 Garand has a particularly long and heavy firing pin. Back in the days when people shot Garands, people had slamfires. It was common knowledge, because you heard about it and could met the people to whom it happened to. There is an Article in American Rifleman where a guy who had a slamfire (with Federal primers) explored how to get a slamfire. His experiments were interesting, but there were things he could not do that would have been even more of more value. He did not look at the kinematics of the system and determine the energy level of the firing pin, and compare it against the sensitivity of commercial primers. High speed cameras are expensive and primer makers don’t release hard data on their primers.

I had a slamfire with a hand seated Federal primer. All of the primers were below the case head. I had not sized the case with a small base die and it turned out that all the cases were just a little long (.002â€) and a little fat. A combination of a sensitive primer and a little delay to bolt closure was enough to cause an out of battery slamfire that blew the backend of a receiver off.

Last year, I was talking to a gentleman who had a Wilson Barrel installed on a Garand, This barrel was installed by a gunsmith who final finished the chamber with a commercial reamer. Commercial reamers are tighter than military. The shooter was unaware of the peculiarities of the Garand Mechanism, sized once fired brass with a standard sizing die, did not use case gages to measure cartridge headspace, used a Federal primer, and blew the back off his receiver.

His comment to me was that “people ought to be aware how dangerous these rifles are to load forâ€

I have talked to a number of gentleman who had slamfires in Garands. The one common thread was Federal primers.

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.

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 then becomes is that all primers are the same, 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 overally 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.

This thread, about six pages long, has one gentleman's experience about a slamfire.

http://www.thehighroad.org/showthread.php?t=264020

In the summer of 1968 or 69 the Atlantic Fleet Rifle Matches were plagued with slamfires using .308 Match ammo. Seems a terrible long time ago, and I still get upset about it because I lost my best and only chance to leg out on that cartridge. I was in the first relay at 500 yards (not 600 because the Annapolis range only went out to 500), and someone else popped off the first slamfire and dumped a bullet into Chesapeake Bay. I think I was the second or third to do so, and dropped my score from winner to first leather. The range officer did not allow a refire for any of us in first relay. By the second relay, the ammo malfunction was quite evident, and refires were given, but nothing was done for those of us in first relay. Slamfires popped all afternoon, was not a pretty sight. On examination, and believe me everyone was looking at ammo that day, the decision was a batch of overly sensitive primers. I guarantee, a slamfire can run your entire day!!!

Don't count on the bridge in the receiver blocking the firing pin to be 100% effective in preventing slam fires. Remember, the bolt is in contact with the cartridge as it is loaded and the floating firing pin can and does strike the primer each and every time a round is loaded into the chamber. If you doubt this, just chamber a round and then remove it without firing; you will see a slight dent in the primer every time.

All it takes is a sensitive primer, high primer, or cartridge stopping short of full chambering for whatever reason to set 'er off.

Regards,
hm

Sierra2, it sounds like your slamfires were not "out of battery". Is that true?
peter.

A local shooter used some large pistol primers he bought during the primer famine of the Clinton administration. He'd get 1-2 slamfires per clip.

Peter, no, our slamfires occurred when the bolt closed, as in normally releasing the bolt to chamber a round. I've noticed that Garand firing pins always leave a tap on the primer over the years since this accident, an M-1A will do that too. Those primers were just too light to be safe. After thinking about it, we were mostly amazed that none of the rifles went full auto with that ammunition.

quote:

In the summer of 1968 or 69 the Atlantic Fleet Rifle Matches were plagued with slamfires using .308 Match ammo. Seems a terrible long time ago, and I still get upset about it because I lost my best and only chance to leg out on that cartridge.

Sierra2: Bummer! Were you shooting the 7.62 M1 or M14? Understand the navy had some M1's chambered for 7.62...when did they switch over to the M14?

The M1 follower tends to slow the bolt down a bit when single loading but the M14/M1A bolt slams home faster unless single round is loaded through the magazine.

Our AMU was still shooting the M1 in '61 even though some units had received M14's.

Regards,
hm