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PUNJTANI5
19-09-2010, 06:27 PM
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.


p.S
I AM UNABLE TO POST LINK AS THIS INFO IS VERY ANCIENT AND WEBLINK IS NO LONGER AVAILANLE

Starfish
20-09-2010, 12:07 PM
This article falsely states that a slam fire will destroy your gun. A slam fire wont destroy your gun. Can not be much sure about your feet though :p

AK47
20-09-2010, 12:14 PM
This article falsely states that a slam fire will destroy your gun. A slam fire wont destroy your gun. Can not be much sure about your feet though :p

+1! Confused me too! :rolleyes:

Denovo87
20-09-2010, 12:41 PM
This article falsely states that a slam fire will destroy your gun. A slam fire wont destroy your gun. Can not be much sure about your feet though :p

Yes; it can, in case the striker pin hits primer before round is get seated in chamber properly (out of battery detonation).

Starfish
20-09-2010, 01:04 PM
Hmmm. Actually you are right. If the slam fire occurs due to a stuck (in the forward position) firing pin, then this might be the case. An out of battery detonation may occur.
Even though, its highly unlikely. When a round is being fed in to the chamber, it points slightly upwards and the primer is pointing downwards to help with the feeding. The primer may only come in contact with the PIN when the round it almost seated and its angle is parallel to the firing PIN.

otherwise the forward motion of the floating PIN will probably occur when the bolt stops in the forward position and the firing PIN is accelerated forward due to the inertia.
Coming back to the out of battery firing. Lets consider the fixed firing PIN, open bolt type weapons. How do they function? I think the bolt slams forward hitting the primer with its fixed firing PIN. How do they prevent out of battery firing with this mechanism? What about API weapons?

Skeeter60
23-09-2010, 12:45 PM
A SLAM FIRE CAN AND WILL DESTROY A GUN AND HURT SERIOUSLY IF AND WHEN THE SLAM FIRE OCCURS BEFORE THE RIFLE / AUTO PISTOL HAS HAD A CHANCE TO LOCK UP.
When the chambering is complete at the same time the locking of the bolt takes place in auto rifles and pistols. Generally quality weapons will have firing pin blocks which prevent the firing pin from moving forward unless the Rifle /pistol bolt/slide is locked and the trigger pulled fully back.
Firing pin blocks exist on on free floating firing pins as well but some do not like the Dragunov, the Dragunovs blow up when US hunting ammo and reloads are used as the original military round has a very hard primer.
Some times when we slam a bolt forward on an auto rifle and then extract the loaded round we will find a small primer indentation on the primer, it is not enough to fire the round; but Murphy said "If anything can go wrong, it will ".
There was once a problem with POF 12 gauge cartridges where the primer was seated too deeply and Beretta auto shot guns were not firing it. Some Homeopathic engineers had the firing pins elongated ( it straight away voids the warranty) and can result in a slam fire. The Beretta has a lovely safety feature, the pin can only go forward when the tilt locking is complete, in that case the gun can still slam fire but will not self destruct.
Always point a gun in a safe direction

Starfish
23-09-2010, 01:11 PM
Curses for the murphy! :)