My M305 went kaboom
- Thread starter beavis_m305
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captainamazing
CGN Regular
- Location
- The Socialist Autocracy of Canada
Damn!! I just EMT'd him $500 for a "slightly exploded" but otherwise mint condition M305.
Damn!! I just EMT'd him $500 for a "slightly exploded" but otherwise mint condition M305.
I'm sure it'll buff out pretty easily.
This is what's making me scratch my head too. I understand how an improperly retracted or stuck firing pin might cause the gun to fire out of battery, but I don't understand how it could have made the gas system come loose.
beavis_m305
Regular
- Location
- New Zealand
Your quite right about the case length (doh!), I had never really thought about it. I'll PM the dude that did it. To pose the question for clarity on my part - upon undoing the gas lock, is it normal to be able to grasp the remaining gas cylinder and pull it forward along the barrel towards the flash hider?
autocrash
CGN Regular
My understanding is yes, it is normal to be able to move the gas cylinder along the length of the barrel (how else would you remove it for cleaning??) (Mine slid right off when i disassembled it for the first cleaning...)
I wouldn't worry about that... but the handguard coming off might be a concern... I'd have a gunsmith take a close look at the chamber area... but it sure sounds like it was just out of battery slamfire....
X2. That part isn't significant. Have you stripped your bolt down and inspected the firing pin for obstructions or build-up? I always have lots of brass shavings everywhere after a while... (sorry if you already stated)
Just my two cents. Let me clarify, I have not ever had a slam fire with my rifle.
The pictures you provided are tell the story. There is one picture missing, and that is one of the bolt. particularly one showing the the right lug.
The picture showing the right locking lug had received a tremendous force applied diagonally on the face closest to the bolt lug. I noted in the first set of pictures, that the lower portion of the left lug also appears to have sustained a shear as well. The interesting issue was the split casing, popped primer and the gas block "jumping" the threads.
Assuming a slam fire occurred, upon contact with the firing pin to the primer, a chain of events would now occur within a fraction of a second.
1) The bolt travel is only partially locked when the firing pin causes the primer to ignite and "spray" hot gas into the casing.
2) The powder would start to ignite and pressure would start to rise steeply within the casing.
3) At the same time, the expanding gasses from the powder/primer would now cause the pressure forces to begin to act on the casing walls and primer pocket in a multi-directional manner from the area of initial powder ignition, or the rear of the casing.
4) The casing reacts by yielding when force of the building pressure exceeds the elasticity limit of the brass, and the case fails. At this point in time, the case is still inside the chamber and the bolt is only partially locked in the lugs.
5) Additional powder igniting causes more pressure to build within the casing. At this time, the bolt is still relatively secure and the increasing pressure forces the bullet into the barrel.
6) Additional powder ignition and burning causes still more pressure to build and the relatively small surface area of contact between the bolt and receiver lugs exceeds their tensile strength limits and they fail (shear) at those contact points. The bolt now starts to travel rearward.
7) The powder has now fully ignited and the gases expand in two directions. One towards the rear of the rifle and the forward of the chamber.
8) The rearward pressure exits the split casing and pushes the bolt back like a piston. At the same time the gas also vents violently multi-directionally and resulting pressures exceeds the limits of other components, such as the magazine, the receiver itself and the scope mount. Under the strain and stresses, some of the materials fail...such as the magazine, or contort/stretch...such as the receiver.
9) The forward pressure continues to build and exerts sufficient force to push the bullet out the barrel, and at that point. All gases have either vented out the barrel or gas block.
10) The force exerted on the bolt causes a buildup of momentum on the bolt and it slams rearward in the receiver. The extractor pin during this action would extract the casing head.
11) The smoke would clear, and you'd exclaim..."What the hell?!?"
The jumping of the handguard is likely the result of the violence of the bolt smacking hard against the receiver and the resulting contortions/elasticity of metal in the rifle. Look at some really slow motions of an AK firing and you'll see what I mean.
I doubt the primer popped out, rather, with all the casing deformation, it was more likely "thrown" from the primer pocket. Remember that when the forces of the expanding gasses are acting on the bolt, they would likely have firstly pushed the primer rearward due to inertia, until it made contact with the bolt, then these same same forces would have acted on the the casing head, pushing it onto the bolt face as well. This would have occurred prior to the bolt failing, so the primer and split case head would be "resting" on the bolt face.
The interesting fact was that you stated that the gas assembly had "jumped" off their threads. In my opinion, that would be quite impossible, assuming the nut was secured, even hand tight. The pressures at that point along the barrel would be no where near normal operating pressures under normal operating conditions. To "jump" the threads, as it were, the gas block was either grossly out of spec, or was hanging onto only the last one or two threads. If that was the case, the rifle would have had some cycling issues, as most of the gases would have vented outside rather than be fully directed onto the piston.
One other thought was that cartridge itself was not in spec. While you were clear to mention that the ignition happened once you released the op rod, you also stated that you loaded two more rounds into the magazine. Does this mean that the magazine was in place and you reloaded from the top? Was it possible that the neck of the casing somehow got damaged in that process and resulted in the casing not being able to fully chamber, which would then result in the bolt only being partially closed? I ask because with a bolt gun, I once exerted too much force on loading a bullet into the rifle, with the bolt not fully retracted, and the result was that I damaged the casing. The bolt would not close, kinda like when you use a field headspace gauge on a new rifle.
With an M14, you would never know there is not an issue if you are not fully familliar with how it sounds when loading, etc.
Just my thoughts.
The interesting
The pictures you provided are tell the story. There is one picture missing, and that is one of the bolt. particularly one showing the the right lug.
The picture showing the right locking lug had received a tremendous force applied diagonally on the face closest to the bolt lug. I noted in the first set of pictures, that the lower portion of the left lug also appears to have sustained a shear as well. The interesting issue was the split casing, popped primer and the gas block "jumping" the threads.
Assuming a slam fire occurred, upon contact with the firing pin to the primer, a chain of events would now occur within a fraction of a second.
1) The bolt travel is only partially locked when the firing pin causes the primer to ignite and "spray" hot gas into the casing.
2) The powder would start to ignite and pressure would start to rise steeply within the casing.
3) At the same time, the expanding gasses from the powder/primer would now cause the pressure forces to begin to act on the casing walls and primer pocket in a multi-directional manner from the area of initial powder ignition, or the rear of the casing.
4) The casing reacts by yielding when force of the building pressure exceeds the elasticity limit of the brass, and the case fails. At this point in time, the case is still inside the chamber and the bolt is only partially locked in the lugs.
5) Additional powder igniting causes more pressure to build within the casing. At this time, the bolt is still relatively secure and the increasing pressure forces the bullet into the barrel.
6) Additional powder ignition and burning causes still more pressure to build and the relatively small surface area of contact between the bolt and receiver lugs exceeds their tensile strength limits and they fail (shear) at those contact points. The bolt now starts to travel rearward.
7) The powder has now fully ignited and the gases expand in two directions. One towards the rear of the rifle and the forward of the chamber.
8) The rearward pressure exits the split casing and pushes the bolt back like a piston. At the same time the gas also vents violently multi-directionally and resulting pressures exceeds the limits of other components, such as the magazine, the receiver itself and the scope mount. Under the strain and stresses, some of the materials fail...such as the magazine, or contort/stretch...such as the receiver.
9) The forward pressure continues to build and exerts sufficient force to push the bullet out the barrel, and at that point. All gases have either vented out the barrel or gas block.
10) The force exerted on the bolt causes a buildup of momentum on the bolt and it slams rearward in the receiver. The extractor pin during this action would extract the casing head.
11) The smoke would clear, and you'd exclaim..."What the hell?!?"
The jumping of the handguard is likely the result of the violence of the bolt smacking hard against the receiver and the resulting contortions/elasticity of metal in the rifle. Look at some really slow motions of an AK firing and you'll see what I mean.
I doubt the primer popped out, rather, with all the casing deformation, it was more likely "thrown" from the primer pocket. Remember that when the forces of the expanding gasses are acting on the bolt, they would likely have firstly pushed the primer rearward due to inertia, until it made contact with the bolt, then these same same forces would have acted on the the casing head, pushing it onto the bolt face as well. This would have occurred prior to the bolt failing, so the primer and split case head would be "resting" on the bolt face.
The interesting fact was that you stated that the gas assembly had "jumped" off their threads. In my opinion, that would be quite impossible, assuming the nut was secured, even hand tight. The pressures at that point along the barrel would be no where near normal operating pressures under normal operating conditions. To "jump" the threads, as it were, the gas block was either grossly out of spec, or was hanging onto only the last one or two threads. If that was the case, the rifle would have had some cycling issues, as most of the gases would have vented outside rather than be fully directed onto the piston.
One other thought was that cartridge itself was not in spec. While you were clear to mention that the ignition happened once you released the op rod, you also stated that you loaded two more rounds into the magazine. Does this mean that the magazine was in place and you reloaded from the top? Was it possible that the neck of the casing somehow got damaged in that process and resulted in the casing not being able to fully chamber, which would then result in the bolt only being partially closed? I ask because with a bolt gun, I once exerted too much force on loading a bullet into the rifle, with the bolt not fully retracted, and the result was that I damaged the casing. The bolt would not close, kinda like when you use a field headspace gauge on a new rifle.
With an M14, you would never know there is not an issue if you are not fully familliar with how it sounds when loading, etc.
Just my thoughts.
The interesting
beavis_m305
Regular
- Location
- New Zealand
I think we can rule out everything I've mentioned about the gas system.
I got enough time after work today to strip her down again and get some photos of the bolt and left locking lug. Uh oh... I can't believe I didn't pick up on this damage. In my defense the last time I looked at the bolt I was still in a slight state of mind #### over what just happened. Anyway it doesn't look pretty at all...
You can clearly see that both bolt lugs are gouged, as well as the left locking lug. I'm sending it back to the shop to see if they'll do some kind of warranty. I do not want to fire this rifle with critical areas looking like that
I got enough time after work today to strip her down again and get some photos of the bolt and left locking lug. Uh oh... I can't believe I didn't pick up on this damage. In my defense the last time I looked at the bolt I was still in a slight state of mind #### over what just happened. Anyway it doesn't look pretty at all...
You can clearly see that both bolt lugs are gouged, as well as the left locking lug. I'm sending it back to the shop to see if they'll do some kind of warranty. I do not want to fire this rifle with critical areas looking like that
That damage on the bolt makes more sense to me. If the gun fired out of battery, before the lugs locked, a whole lot of force had to go somewhere...
Just be glad you're OK, and see if the seller will stand behind it. Good luck.
Just be glad you're OK, and see if the seller will stand behind it. Good luck.
What was the outside temperature when this happened? the reason I'm asking is that if there was grease or cosmo on/around the firing pin, it may have been soft enough to safely cycle rounds when you were warm and indoors, but if it was cold out, it could have caused the grease to stiffen up just enough to let the pin detonate the primers??????
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