Post mortum LE bolt failure...

Remember some of this factory ammo has been around since before our time. Some of it has been cooked in various deserts and storage facilities for years and then purchased by gun dealers for sale in another area. This ammo is well known for it's unreliability. It can create a bomb waiting for detonation...maybe it was the light loads, but I'd suspect the wheel was spun and the cooked surplus factory round came up. I doubt the OP or the rifle owner can even tell us reliably what the cartridge was...guess work...he'll likely not sort this out for sure.

Based on the very limited info it doesn't appear that either the bolt locking lugs or the shoulders in the receiver failed yet the quote from the shooter indicates the separated rear portion of the bolt flew back with some velocity! A simple stress concentration and associated crack near the lugs (due to heavy overpressuing) couldn't cause that, could it? Something had to drive that separated portion rearwards. But if blown primers, at worst, can only set things back to the half-bent, then what could do it?

Ridolpho

Maybe the "light loads" succeeding in plugging the barrel with a few bullets.

The first factory load then creates a massive over-pressure. Possibly the front part of the bolt has been blown out of battery with the chamber, and in doing so has pivoted around the bearing faces at the locking lugs. The back part of the bolt is then being pressed against the unyielding base of the boltway - thus bending and fracturing the bolt body at the pivot point.

I bet there is the whole story to be deduced, if photos of the bolt & cartridge cases were to be posted...

But I'll bet a pound to a slice of xxxx that even with this catastrophic (?) failure, the bolt didn't lift and open.

Actually, in mechanical engineering investigative terms, it wasn't a true catastrophic failure eitherwas it. It held firm. Just a point to ponder!

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Originally Posted by Thunderbox

succeeding in plugging the barrel

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That would do it...

if he shot an under pressured round and/or a did not seat the bullet right with the hand loads and plugged the barrel then fired another round i would expect a lot more serious failure. like a blown up chamber.

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Originally Posted by mrbungle

if he shot an under pressured round and/or a did not seat the bullet right with the hand loads and plugged the barrel then fired another round i would expect a lot more serious failure. like a blown up chamber.

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IIRC no-one has ever reported such a thing; maybe the chamber and receiver ring are the least likely to fail as they have the greatest structural strength?


Maybe someone else remembers a Canadian (?) website where they described a destruction test of an SMLE? They had a barrelled action, where the action had already been "weakened" by having been drilled through the wall multiple times for scope mounts. They ran an experiment to try and cause the rifle to blow up by blocking the barrel. IIRC, mud, snow and other "service use" bore obstructions had no effect whatsoever.

They then tried hammering some bullets into the bore, but these got blown out, leaving some bore bulges. Finally they started hammering metal spikes into the muzzle. Apparently, on each firing, the section of barrel containing the spike fractured and came off, leaving the remainder and the action still serviceable. IIRC they finished the rifle off by using a spike in the bore and some cartridges filled with Bullseye or some pistol powder. Finally, the receiver gave way in the usual SMLE fashion - bending and distorting so that the bolt could not be cycled. They could not cause a catastrophic event, and the chamber section of the barrel remained intact.

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Originally Posted by breakeyp

I am not a handloader and do not intend to. From what I have read, reduced handloads can be very dangerous

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In some cases yes, but thats when your using a reduced rifle powder charge, I,ve been downloading for some time but use fast burning pistol powders, I,ve experimented with over charging and under charging the case, (all done under controlled conditions) with me standing a great distance away.

I suspect one of the light loads was too light, and may of left a bullet in the barrel, TB mentions the SMLE and blocking the muzzle end to try and blow the rifle, I would think the chamber end blockage may of been at fault... a common problem with handloading is a lack of charge in the case, the primer will push the bullet so far.... cant remember how far, as I havent done that for many years.

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Originally Posted by browningautorifle

Remember some of this factory ammo has been around since before our time. Some of it has been cooked in various deserts and storage facilities for years and then purchased by gun dealers for sale in another area. This ammo is well known for it's unreliability. It can create a bomb waiting for detonation...maybe it was the light loads, but I'd suspect the wheel was spun and the cooked surplus factory round came up. I doubt the OP or the rifle owner can even tell us reliably what the cartridge was...guess work...he'll likely not sort this out for sure.

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No doubt about it Jim, you could be correct. But we will never know, he could have been talking about current production civilian ammo like that sold by Remington and several others, fresh from the factory.

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Originally Posted by breakeyp

It was explained to me that there is a balance point of powder vs. available oxygen in the cartridge case. Less powder in the case and more air caused a "double detonation" which increased chamber pressures. A crack was started and full loads finished the lot off. Perhaps more knowledgeable people can expand on this.

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Firstly I'm NOT "more knowledgeable" on this subject but this is my understanding.
A case with plenty of powder will cover the primer so when detonated the "front" of the resultant explosion will travel forward building pressure & so pushing the projectile forward & out the end of the barrel, a case with too little powder will leave the primer exposed & when detonated will/can cause the powder to be ignited at multiple points due to the flash over from the primer, this not only causes virtually all the powder to ignite simultaneously but also multiply "fronts" traveling in different directions which collide causing major pressure spikes.