Failed Krag bolt-lug

[butlersrangers]

Mark Daiute kindly offered a model 1892 Krag-bolt, with a cracked lug, to an interested KCA member, for the asking.

I asked for it, and the 'cracked bolt' arrived, yesterday. I took some photos of it today.

We don't know the exact story, about what caused the bolt to break.
It likely failed from a diet of cartridges that generated excessive pressure.

The fracture line followed the usual "C" curve, around the rear of the lug and extending on both sides to the bolt face & flange.

Some of the pictures show the failed-bolt contrasted with a 'new' original bolt.

A 'pending crack', hidden below the hardened surface, will likely show a 'wrinkle' under the surface 'skin', (following this same pattern), before the lug openly cracks like this one, did.

Thanks Mark for sharing this example!

[psteinmayer]

Now there's a bolt that has seen it's fair share of abuse!

[scottz63]

Pretty amazing that the last shot fired with that cracked bolt did not snap the lug completely off. Krag tough I suppose.

[ebruce]

Never seen such a thing! Thought that a cracked bolt would be completely missing the lug. Amazing that this bolt held even with such a large crack. Sincerely. bruce.

[FredC]

As expected in an overload. Hard surface case with soft/tough core material. I am suspecting a single overload event with the lip surrounding the case rim blown out like that. Maybe the bolt squirmed when the lug cracked but escaping gas taking out that lip by the rim seems more likely to me.

[King carp]

Some JB weld and off to fleabay.(just kidding)

[butlersrangers]

Mark reports that the early bolt came with a barreled action he purchased.

He used the rig to shoot mild cast-cast bullet loads, with good results.

The cracked lug developed after firing a few 220 grain 'jacketed' loads, (using data from the Speer manual), for IMR-4350.

FWIW - (I suspect the cracks were probably lurking under the surface for some time, before being stressed by a full power load).

Thank goodness for the .30-40 cartridge rim and the Krag's robust 'guide-rib'.

[scottz63]

Thank goodness for the .30-40 cartridge rim and the Krag's robust 'guide-rib'.

I was looking at mine and thinking that the 'guide-rib' should act a a very good safety lug.

[butlersrangers]

The late Michael Petrov conducted 'destructive tests' of a U.S. Krag action which were rather remarkable.
His 'test action' had the bolt's 'locking-lug' entirely removed!

The guide-rib/'safety lug', alone, bore the force of some grossly powerful abusive loads.

IIRC - The barrel threads eventually stripped, the receiver broke, but the badly damaged bolt remained 'wedged' in place!

Searching the KCA Forum pages, I found a picture of Mark Daiute's early bolt, when he first obtained it in 2023.

The photo angle doesn't reveal the pending 'cracks' to the lug, but, it may show flaws in the bolt-face flange.

[butlersrangers]

Mark's 1892 bolt (2023 & 2024) contrast: