Mosin 91 bolt cracked and busted

It looks like the bolt head did not rotate when the bolt body was turned up.

The locking lugs on the bolt head could be seriously set back into the locking shoulders in the receiver.

You should be OK on headspace, as it's a rimmed cartridge. Also OK on any old Mosin bolt. I've got three different models and their bolts all interchange. But ... that's just my own opinion from my own experience and I'm no Mosin expert and not a gunsmith.

Never seen anything like that. Glad no one was hurt. I also would like to know whats up. I have about 20 Mosins.

In addition to dealing with the bolt, have you some idea what kind of ammo was in the chamber when it went off? Perhaps a bad handload, or a dodgy batch of surplus ammo? Have you taken the action out of the stock to see if there was any other damage?

Is the bolt serial mismatched? It might just be a poorly-hardened bolt installed by the importer. Matching numbered surplus Mosins are generally pretty well-used and should have failed before now however, so in that case I'd want to rule out any ammo-related issue.

This is interesting.

A quick internet search shows the apparent number of documented Mosin destructive failures can be counted on one hand.

.455_Hunter said:

A quick internet search shows the apparent number of documented Mosin destructive failures can be counted on one hand.

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Any missing fingers on that hand!?!?

sorry - any good opportunity to be a wise-ass is an opportunity I just can't pass up

That looks like a gunsmith trip is in order. A check for headspace would be a good idea just to be safe. Mosins are one of the most robust firearms I have ever worked on so it would be interesting to figure out why the bolt failed.

Thats a first.

Your bolt is still locked. Without the bolt handle bar camming the bolts lug that rides there, nothing is rotating it out of lock.

To fail in that place had no pressure, it must have been cracked already. Hopefully your lugs are not set back.

I would pop off the busted piece and work the bolt out, if possible.

Have a good hard look at the case, the base of it, and the primer. Thats where you can see if you have excessive pressures.

Its a rimmed cartridge, the headspace is set on the Rim. You can change bolt or just the bolt head and be just fine.

Get 'er out and post picts!!!

You may have to unscrew the barrel to get the bolt and case out.

H....HOW!?

I agree with Caribou now that I looked at it again. I think it,s a fatigue issue, not a pressure one.

Pivot Dr said:

You may have to unscrew the barrel to get the bolt and case out.

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You ever tried removing a barrel from an old Mosin?? Royal pain in the arse!!
I've seen a few twisted recievers from that..

Sneakshot92 said:

You ever tried removing a barrel from an old Mosin?? Royal pain in the arse!!
I've seen a few twisted recievers from that..

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It isn’t more than scrap iron right now, regardless of how difficult it is, you still might have to unscrew the barrel. There are ways to heat actions without ruining them. It’s a problem, no doubt about it. Wasn’t easy getting the barrel off my 1898 Springfield either but I did get it off.

It shouldn't be hard to remove at all, start with breaking off the broken part. Some prying with a screwdriver to rotate the bolt head up, plying the screwdriver to the lug, while lifting as usual on the bolt handle at the same time.

The connecting bar is still engauge and pull the bolt head back once rotated.

Your not going to have to worry about ruining anything except some finish.

Also, dont forget that the extractor is still holding the case, and you will be having to apply some gentle but firm force.

Once the bolt head is rotated up, if it wont pull back out with the bolt, you can always drive out the case and bolt with a rod and a couple smacks.

failure screams powder degradation, unless you suspect otherwise. I wouldn't use more from that lot.

Just looking at the lug on the bolt head there , and it does not look like it was thrust back at all or enough to crack the bolt handle base.
If your bolt head was set back into the lug areas, you will see other pressure related cracks, folds/stress on the collar, and the lug that would have transferred back to the bolt handle.
The crack seems to be in a way that indicates it was forced up against a stuck case, either over pressured or a dirty "Sticky" chamber. The crack is at a thin point and the lug on the bolt head in the camway could have been what was forced against that piece during bolt lift and unlocking.

Or bolt handle body base was flawed and failed when it did.....

Todd.

I have been mulling that picture over since I first saw it so I looked at a few of my Mosin bolts in the various stages of cocking and locking. I do not understand how this could have been caused by simply firing the weapon. The extractor is below the lug and the lug does not have any factor in locking the bolt so I don't see how it could have been damaged by over pressure in the chamber. The lug on the bolt face is visible below the bent portion of the bolt handle (which the broken segment is a part of) so either a lot of force was applied to operate the bolt after firing or it has been subjected to a lot of force over a period of time and had a flaw from either the machining of the bolt lug or a flaw in the structure of steel used in the manufacture of the bolt.

It almost certainly is a flaw in the metal or fatigue.

The bolt head is the only part of the bolt that contains any pressure aside of a critical failure which would bring the bolt body into gas venting and locking.

The forward part of the bolt root has a number of kinda rectangular cuts. A crack probably originated in there somewhere.

What would the damage pattern be like after a fire out of battery event?

MartinS said:

What would the damage pattern be like after a fire out of battery event?

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Ive never heard of one....yet.

Would be interesting, for sure. maybe Hatcher blew a couple up in his research?

Extremely unlikely to have a out of battery firing. The firing pin is keyed with the firing pin guide so it would be extended only with lock-up.