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Slam Fires on M1 Garands, M1A's, FN-LAR's, SAT-48's and M1 Carbines
Slam Fires on M1 Garands, M1A's, FN-LAR's, SAT-48's and M1 Carbines
The following information is based on an article in the October, 1983 edition of American Rifleman entitled "The Mysterious Slam-Fire." Because this is so important to shooters of the above weapons, Springfield Armory sent a reprint of that article. Since many shooters do not get to see this information, Combat Arms is providing the salient or main points to consider.
Slam fires occur when the bolt closes and, without the trigger being pulled, the round that was chambered fires and destroys the gun. An analysis of these problems seems to indicate that:
1. Commercial primers are more sensitive than military primers. When the bolt slams closed, the free floating firing pin will contact the primer. Normally this should not be a problem. However, if the round is a reload and the primer is incorrectly seated, that may cause the slam firing to occur.
2. If you are a reloader, another problem to watch for is an improperly sized case or one in which the bullet is not seated to the correct depth, making the overall case length too long. A properly sized case will enter the chamber under finger pressure. Never fire a round that fits tightly in the chamber. Never fire reloads in a gun that is under warranty. It voids the warranty!
3. On guns that have had their hammer hooks stoned (match grade firearms), if the stoning was excessive, that can contribute to the slam fire. People stone the hammer hooks to remove excess trigger creep. It should never be attempted except by a qualified armorer or gunsmith. Also use caution in modifying the ejector, extractor or extractor spring. If the ejector is too short or the extractor spring too weak, the bolt cushioning is lessened and consequently, bolt momentum to the head of the cartridge case is increased. Again, this sort of work should be performed by a qualified armorer or gunsmith.
4. Watch for impending case separation if you are reloading. Look for "stretch marks" on the cases. These indicate an impending case separation. Destroy these cases by crushing them flat with a hammer. Also watch for a bright high pressure ring forming ahead of the case web.
5. Remove the firing fin occasionally and clean the firing pin recesses in the bolt. This prevents the firing pin from sticking.
6. Lubricate with Break-Free CLP (TM). This is one of the finest cleaners, lubricants and preservatives ever made. If you do not know how to properly clean your weapon, then do not be shy. Contact your local gun shop and hire someone there to teach you how to do it properly.
7. Always wear shooting glasses! You have been given one set of eyes in this life. If the gun literally explodes while you are holding it, you could lose your eyesight. Safety glasses are very inexpensive ($4.95 to $29.95).
As you can see, the biggest factor affecting slam fires is reloaded ammunition. In my humble opinion, based on being a shooter and gun store owner, not one reloader in 100 knows how to properly reload. The biggest reason is that the remaining 99 out of 100 do not carefully study the reloading manual and follow instructions. There are many ways to reload and only one or two correct ways.