Slamfires
- Thread starter SHusky57
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A slam fire occurs because the firing pin continues to move forward under inertia as the bolt closes.
This happens mostly (only?) with guns that use a free-floating firing pin, such as the M1 Garand or SKS. Having a soft primer on the ammunition also contributes to it.
Most, if not all, pistols made now have a firing pin block that prevents the pin from moving forward unless the trigger is pulled. Many also have firing pin springs that prevent the firing pin from moving too far forward under inertia.
This happens mostly (only?) with guns that use a free-floating firing pin, such as the M1 Garand or SKS. Having a soft primer on the ammunition also contributes to it.
Most, if not all, pistols made now have a firing pin block that prevents the pin from moving forward unless the trigger is pulled. Many also have firing pin springs that prevent the firing pin from moving too far forward under inertia.
ArfinGreebly
Moderator Emeritus
Slamfire vs Chainfire
I've heard the term "slamfire" used to describe two kinds of thing: 1) weapon firing prematurely when the slide/bolt closes, and 2) rounds in a tubular magazine setting one another off.
I believe the second case is properly called "chainfire."
A slamfire can be cause by a seized firing pin, rusted (or "gummed") to the bolt so that it's always exposed and always engaged, so that simply closing the bolt hard causes the firing pin to strike the primer.
There may be other variations, but I think that gets us started.
I've heard the term "slamfire" used to describe two kinds of thing: 1) weapon firing prematurely when the slide/bolt closes, and 2) rounds in a tubular magazine setting one another off.
I believe the second case is properly called "chainfire."
A slamfire can be cause by a seized firing pin, rusted (or "gummed") to the bolt so that it's always exposed and always engaged, so that simply closing the bolt hard causes the firing pin to strike the primer.
There may be other variations, but I think that gets us started.
ljnowell
Member
Every slamfire I have ever seen was caused by a filthy gun that had a firing pin siezed.
The Lone Haranguer
Member
Some older pump shotguns, e.g., Winchester 97, allow slam firing. Hold the trigger down and cycle the action, and the gun will fire when the forend is slammed forward. This is of little actual use except in very close quarters battle with multiple assailants, but it can be done.
bigalexe
Member
What Lone Haranguer said was what i was going for and i have one thing to add.
While some shotguns are capable of doing this it isnt very nice on the gun and from what ive heard you stand a better chance of breaking the gun than doing any real damage downrange.
While some shotguns are capable of doing this it isnt very nice on the gun and from what ive heard you stand a better chance of breaking the gun than doing any real damage downrange.
MattTheHat
Member
It can also be done on some pump action rifles, such as the Taurus Thunderbolt.
-Matt
-Matt
I have a squeaky clean gun with a clean free floating pin (SKS) that will slam fire with non-military surplus ammo. I am in the process of replacing the free floating pin with a spring loaded pin. I shot hundreds of military surplus through it with no problems, but if I put your run-of-the-mill Winchester in it, it WILL slam fire.
ljnowell
Member
I believe clean guns will do it too, just from personal experience it was caused by sloppy owners.
Not sure it would be considered a slam fire, but I had a bad trigger job, and the hammer followed on me. Had a nice hole in the floor from it. 
Spent a ton of money tricking out that gun, and even after repair with 2k trouble free rounds through it I couldn't get comfortable carrying it. 
Spent a ton of money tricking out that gun, and even after repair with 2k trouble free rounds through it I couldn't get comfortable carrying it. Shadow 7D
Member
can also refer to something going of half cocked when dropped, take the M-249, it has a hangup at about 3/4 cock, feels like the real thing, except that when it get bumped, it goes boom.
Zwetschgen
Member
I think it is safe to say that revolvers cannot slam fire, but blackpowder revolvers can chainfire. If burning powder or the sparks from one cap reach the powder of another chamber, both/multiple will fire, surely doing damage to your pistol. As stated before any free floating firing pin weapon could slam fire, either intensionally or accidentally. You could conceivably wedge the firing pin foward which would make your firearm fully automatic (so to speak) but if the firing pin is lodged forward it will fire without stopping until the magazine is empty. I've never heard of any modern pistol (like glocks) slam firing, but if they have free floating firing pins, they could.
rcmodel
Member in memoriam
Glocks couldn't because the striker is so light it would have practically no momentum.
Certainly not enough to set off a primer.
Most other handguns use the basic John Browning design, and depend on the round in the magazine sliding up under the extractor as it feeds.
If the firing pin were sticking out of the breach-face, it would stop the round dead in it's tracks before it got out of the mag and into the chamber.
Other guns, like the Russian MAK, pop the round into the chamber before the extractor has control of it. They can fire or even go full auto if the firing pin were stuck in the foreword position.
Still other guns like the AR-15 mechanically retract the firing pin out of the bolt as it unlocks. It can't reach the primer until the bolt locks again.
The M1 Garand. M1 Carbine, M-14, and Ruger Mini-14 employ an L-bend on the rear end of the firing pin that must fit through a slot in the receiver before the bolt can finish locking.
rc
Certainly not enough to set off a primer.
Most other handguns use the basic John Browning design, and depend on the round in the magazine sliding up under the extractor as it feeds.
If the firing pin were sticking out of the breach-face, it would stop the round dead in it's tracks before it got out of the mag and into the chamber.
Other guns, like the Russian MAK, pop the round into the chamber before the extractor has control of it. They can fire or even go full auto if the firing pin were stuck in the foreword position.
Still other guns like the AR-15 mechanically retract the firing pin out of the bolt as it unlocks. It can't reach the primer until the bolt locks again.
The M1 Garand. M1 Carbine, M-14, and Ruger Mini-14 employ an L-bend on the rear end of the firing pin that must fit through a slot in the receiver before the bolt can finish locking.
rc
Black Dime
Member
There are quite a few shooters in SASS that consistently slam fires the 97. There are some who (including gunsmiths) remove the action lock to be able to slamfire more easily.
There are a number of new single actions that do not have the transfer bar. Colt has never used it except in a cheapo SA that they imported. I am pretty sure S&W does not use the transfer bar.
There are a number of new single actions that do not have the transfer bar. Colt has never used it except in a cheapo SA that they imported. I am pretty sure S&W does not use the transfer bar.
rcmodel
Member in memoriam
S&W doesn't need to use a transfer bar.
They use a tried and true system that employs two positive hammer block safety systems. Even if one should fail, the other one would still work.
One blocks the hammer from moving from underneath with the steel rebound slide.
The other inserts a solid steel block between the hammer & firing pin at all times, unless the trigger is pulled to the rear.
rc
They use a tried and true system that employs two positive hammer block safety systems. Even if one should fail, the other one would still work.
One blocks the hammer from moving from underneath with the steel rebound slide.
The other inserts a solid steel block between the hammer & firing pin at all times, unless the trigger is pulled to the rear.
rc
A slam fire could also happen if you dry fire a lot and the firing pin breaks. The broken half could cock or rotate and jam in the extended position. I’ve cracked a couple firing pins, and the retaining pin on a Ruger Mk. II pistol; it didn't slam fire, but it did leave a light mark on the case just from letting the bolt go forward.
This could happen with any semi-auto, and with any safety system; always point in a safe direction while loading.
This could happen with any semi-auto, and with any safety system; always point in a safe direction while loading.
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