Post mortum LE bolt failure...

[ssj]

Any ideas what happened here?

Attachment 46152Attachment 46153

I can understand a failure on the lugs or before, but after?

Information

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[paulseamus]

Failure has occurred around the bearing surfaces of the lugs.

Is it a result of poor heat treatment during the hardening process of the lugs, or is it just a result of crystalization of the metail over time?

Could also be from poor bolt fit. If only one lug was bearing the load then the bolt will be strained in this area.

[303Guy]

I have no suggestions but being curious I would like to know. Did that break firing a normal round? Milsurp or sporting?

May I keep copies of your pics for my own interest?

[ssj]

Hi, not my pics, someone elses, Im asking the "pros" in here for ideas why. It looks after the lugs in an area I'd expect to be stress free, so Im wondering what happened.

"Prepared it for firing and put some light hand loads through. Stoked with the results I decided to test it against some factory ammo. First round gave a hell of a whack, sticky bolt but no hard extraction or real issues. Thought to myself they must have overcharged that one. Chambered the next something didn't feel right. Had a good soldiers 5 and nothing I could see wrong. Had a shot, crack, safety glasses smashed, bloody sore head and a shattered bolt. It snapped just forward of the bolt handle and sent **** flying everywhere. I've got a few garks on my trigger hand and forearm on the other. By my account I'm lucky to have walked away from that. "

is the decription...

[303Guy]

Wow. Well, I speculate that it would seem like a blown primer driving the striker back with enough force to break off the bolt at the stress point. I had a look at my SMLE bolt heads and although there is a vent hole in them the vent hole is largely covered buy the receiver side wall. The shooter didn't say anything about the primers but he did mention the first full power round being 'hot' (then he carried on firing the others!) It's easy to criticize someone after the fact, I know, but he should have stopped right there.

Anyway, I'm waiting for the guru's to come in to tell us what they think.

[Thunderbox]

Those magic words... "hand loads"...


The whole firing description sounds like massive over-pressure in the rifle.

---------- Post added at 09:23 AM ---------- Previous post was at 09:20 AM ----------

Wow. Well, I speculate that it would seem like a blown primer driving the striker back with enough force to break off the bolt at the stress point. I had a look at my SMLE bolt heads and although there is a vent hole in them the vent hole is largely covered buy the receiver side wall. The shooter didn't say anything about the primers but he did mention the first full power round being 'hot' (then he carried on firing the others!) It's easy to criticize someone after the fact, I know, but he should have stopped right there.
.

Blown primers have very little effect. Sometimes one has enough pressure to put the striker on half-cock, but they usually just blow oil and soot back out around the firing pin and into the shooters face. The pressure levels are insignificant compared to the structural strength of the rifle.

[ssj]

Yeah im kind of going huh? I still dont fathom why it broke so far back, did it bend due to bad lugs and snap? From what I read he said it was factory ammo...

[gew8805]

Those magic words... "hand loads"...


The whole firing description sounds like massive over-pressure in the rifle.

---------- Post added at 09:23 AM ---------- Previous post was at 09:20 AM ----------




Blown primers have very little effect. Sometimes one has enough pressure to put the striker on half-cock, but they usually just blow oil and soot back out around the firing pin and into the shooters face. The pressure levels are insignificant compared to the structural strength of the rifle.

And don't forget that in Post #4 the fellow shooting the rifle said "Thought to myself they must have overcharged that one." Of course there he was talking about the factory ammo. It would seem that the problem came from one of the reloads he fired before.....

[Ridolpho]

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

[Peter Laidler]

High quality/definition photo of the break, cleaned with methylated spirit first would very probably tell the metallurgists here, such as JM and Breaky exactly what caused the fracture but I suspect TBox has it in one! He's certainly on the nail re blown primers. There used to be lots of them with 50's made factory blank for some reason and it'd just foul up the insides of the bolt and occasionally cause a half cock