Reason for ammo failure? (pictures)
- Thread starter lewallen
- Start date
I believe you have a mistaken view of how the Garand type mechanism retains the firing pin. So to start off, I am going to use M1 Carbine pictures. In regards to firing pin retention and a firing pin retraction cam, the M1 Carbine is functionally similar to the Garand/Mini 14/M14.
This is the firing pin. It is totally free floating. The notch at the front is part of the retaining system. The extractor goes through this notch and holds the firing pin within the bolt. This notch is long enough so the firing pin can go forward through the bolt face and impact the primer. The firing pin is not spring loaded in this mechanism nor is there a firing pin block, such as seen in series 80 Colt M1911's.
Because of the six picture limitation on this site I am going to have to break this up into two posts.
Here the bolt fully retracted in the receiver.
Here is the bolt almost fully forward. The bolt has not rotated and nor are the lugs in battery. The firing pin is just touching the firing pin retraction cam.
The bolt lugs have rotated into battery and now the firing pin tang is in line with the clearance notch in the firing pin retraction cam.
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The firing pin is now clear of the firing pin retraction cam notch and if hit by the hammer, can ignite the primer.
It is also capable of hitting the primer through the inertia during bolt closure. That is why in this mechanism, there is almost always a dimple found on the back of the primer of a chambered round. Sometimes the impact energy is enough to cause ignition of a sensitive primer, and as long as the lugs are in battery, this would cause an in battery slamfire.
So for the proposition that it is impossible for this mechanism to have an out of battery slamfire, that is ignition of the cartridge before lug engagement caused by incidental contact between the firing pin and primer. A simple question: What is holding the firing pin from moving forward in the bolt, in its travel between these lines?
It should be obvious is that nothing is holding the firing pin back. Therefore out of battery slamfires are possible because there can be incidental contact between the firing pin and primer before lug engagement.
It is also capable of hitting the primer through the inertia during bolt closure. That is why in this mechanism, there is almost always a dimple found on the back of the primer of a chambered round. Sometimes the impact energy is enough to cause ignition of a sensitive primer, and as long as the lugs are in battery, this would cause an in battery slamfire.
So for the proposition that it is impossible for this mechanism to have an out of battery slamfire, that is ignition of the cartridge before lug engagement caused by incidental contact between the firing pin and primer. A simple question: What is holding the firing pin from moving forward in the bolt, in its travel between these lines?
It should be obvious is that nothing is holding the firing pin back. Therefore out of battery slamfires are possible because there can be incidental contact between the firing pin and primer before lug engagement.
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Based on the evidence presented, which isn't much, I have three possible explanations for the evidence which all seem equally plausible to me.
1. The round before this had a case head separation that left the front part of the brass in the chamber which violently stopped the feeding of the bullet and caused the firing pin to slam into the primer (notice the solid primer hit).
2. The powder inside the round "clumped" in a weird way that caused a delayed pressure spike which burned as the round was undergoing extraction. This secondary pressure spike blew out the sides and separated the front shoulder of the brass.
3. The brass was out of tolerance at the shoulder and jammed hard into the chamber causing an out of battery slamfire.
To differentiate between options 1 and 3, another spent brass ripped in half would need to be found. If it is found it is a sure sign the chamber was obstructed, eliminating 3.
To increase the odds of 2 being reality, more ammo from the same lot must be disassembled to see if powder clumping or other degradation has occurred in the same lot.
And lastly, these explanations are not mutually exclusive, all three conditions that potentially caused the event could exist in the ammunition, weak brass getting ripped in half, powder clumping, and out of tolerance dimensions.
Without further information, I don't think there is much we can do to narrow down what actually happened, but at least we can explain in a logical why how it could have happened.
1. The round before this had a case head separation that left the front part of the brass in the chamber which violently stopped the feeding of the bullet and caused the firing pin to slam into the primer (notice the solid primer hit).
2. The powder inside the round "clumped" in a weird way that caused a delayed pressure spike which burned as the round was undergoing extraction. This secondary pressure spike blew out the sides and separated the front shoulder of the brass.
3. The brass was out of tolerance at the shoulder and jammed hard into the chamber causing an out of battery slamfire.
To differentiate between options 1 and 3, another spent brass ripped in half would need to be found. If it is found it is a sure sign the chamber was obstructed, eliminating 3.
To increase the odds of 2 being reality, more ammo from the same lot must be disassembled to see if powder clumping or other degradation has occurred in the same lot.
And lastly, these explanations are not mutually exclusive, all three conditions that potentially caused the event could exist in the ammunition, weak brass getting ripped in half, powder clumping, and out of tolerance dimensions.
Without further information, I don't think there is much we can do to narrow down what actually happened, but at least we can explain in a logical why how it could have happened.
I agree that is a potential cause, and one that is actually dangerous in this mechanism. If there is anything which delays or prevents lug engagement, such as portions of a previous case left in the chamber, a long case, or a fat case, which halts bolt movement prior to lug engagement, that firing pin is rebounding off the back of the primer, and the action is not in battery. Given one of those rare sensitive primers, what would happen is an out of battery incident.
Regarding someone else's reloads, I strongly agree. Don't do it.
I once loaded about 2,000 rounds of.223 for my brother, with full warning of potential problems. He took the risk.
A few months after I turned the cans over, I found him at a gun show selling my loads. My hair stood on end. A blown case would have some back to him, and as sure as the world turns, he would have thrown me under the bus. I should have made and sign a waiver, with a notary. I have NEVER shared ammo aain. Trust nobody.
Seriously. Never, ever use ammo that you can't trace completely back to origin.
I once loaded about 2,000 rounds of.223 for my brother, with full warning of potential problems. He took the risk.
A few months after I turned the cans over, I found him at a gun show selling my loads. My hair stood on end. A blown case would have some back to him, and as sure as the world turns, he would have thrown me under the bus. I should have made and sign a waiver, with a notary. I have NEVER shared ammo aain. Trust nobody.
Seriously. Never, ever use ammo that you can't trace completely back to origin.
Mini-14 has a different alignment system from the M1 carbine.
Instead of the "ramp" that is a progressive movement block from locked back, to free to fire the Mini-14 has a square cut in the receiver crosspiece. Until the bolt has rotated fully into battery the "tail" of the FP can not pass through the cut in the frame to strike the primer. Even if the trigger is pulled & the hammer released it just taps the rear face of the firing pin into the cross member of the receiver.
M1a/M 14 has a channel cut in the bolt rear face that does a similar job. Again its a square channel, only 2 options full movement or blocked movement, no curve face like your images show in the carbine.
Instead of the "ramp" that is a progressive movement block from locked back, to free to fire the Mini-14 has a square cut in the receiver crosspiece. Until the bolt has rotated fully into battery the "tail" of the FP can not pass through the cut in the frame to strike the primer. Even if the trigger is pulled & the hammer released it just taps the rear face of the firing pin into the cross member of the receiver.
M1a/M 14 has a channel cut in the bolt rear face that does a similar job. Again its a square channel, only 2 options full movement or blocked movement, no curve face like your images show in the carbine.