SMLE bolt will not unlock.

Hello all, first post and looking for help!
I have a problem with a bolt on one of my rifles - it will not unlock unless I cock it first, then it will unlock.
I inserted the bolt without the bolt head attatched and same problem, it starts to unlock and then gets physically stuck, pulling ther cocking piece out lets the bolt release.
I am making a tool right now to dismantle the bolt ( my number 4 tool is too big)
Any insight as to what to look out for?
I tried a different bolt and that worked fine, put the problem bolt in another rifle and the same thing happens.
Thanks in advance.
Rob.

Until I read your experiments with the bolt, I thought it would be the safety. There are many ways to reassemble the safety but only one is correct. To check this. remove the safety and see if the problem goes way.

Broken cocking piece and the safety stud of the cocking piece is engaging with the safety stud aside the unlocking cam of the bolt?

Worse than I thought, matching numbers bolt too.https://www.milsurps.com/images/impo...olt054vi-1.jpg

Nearly right...... Broken safety stud on the bolt and not the cocking piece! Don't worry about the matching bolt Jag man. We used to fit and re-number bolts every day of the week when required for various reasons. Just so long as it is done absolutely correctly and by someone who knows what he's doing, then that's as good as it gets

Will try and salvage this bolt before I replace it, great diagnosis Peter, thankyou.

You won't be able to salvage that bolt Jag man. That safety stud is what we call a 'safety related part' and shopuld not ever be tampered with. It is particularly hard (and tough) and that's probably the reason why it fractured. Bolt change is the only answer

are there an un-stamped un-issued SMLE bolts floating around like the No4s?

Quote:

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Originally Posted by ssj

are there an un-stamped un-issued SMLE bolts floating around like the No4s?

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Yes there are. Springfield Sporters has new bolt bodies from Lithgow and BSA (1950's production) available.

Quote:

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Originally Posted by Peter Laidler

You won't be able to salvage that bolt Jag man. That safety stud is what we call a 'safety related part' and shopuld not ever be tampered with. It is particularly hard (and tough) and that's probably the reason why it fractured. Bolt change is the only answer

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What does it actually 'do'.
The rifle half cocks, full cocks and fires, it will just not unlock unless I pull back on the cocking piece, I am talking about dry firing - have not shot this rifle.
Ps. Is there a book that covers this in detail?

Someone good at computer graphics should do up a nice video of the action in operation.

The way I understand it is the safety stud on the bolt prevents the striker from accidentally going forward if the bolt is not fully closed or fully open. In such an event this lug will contact the one on the cocking piece and rotate the bolt one way or the other depending on exactly where it was to begin with. A sheared safety lug is a serious problem but I don’t think that by itself would cause the bolt to lock closed, and someone please correct me if I’m wrong. Could the long cocking groove on the underside of the bolt or the cocking piece lug be damaged also? There’s a lot of leverage going on in that spot as the bolt is opened.

A likely scenario is that someone tried very hard to open the bolt with the striker assembly at "half-bent". This could not only shear the bolt's safety lug but also mash the cocking piece's safety lug sufficiently to prevent the assembly camming smoothly from fired (long cam notch) to open (short notch) position.

This all gets much easier to understand if one takes an undamaged bolt assembly out of the rifle and twists/pulls the cocking piece about while observing the interplay of safety lugs and cam notches/slots. There's a much more complex dance going on in there than the uninitiated might think.

I apologise before I even start if this sounds a tad smug. So apologies first. A skeletonised rifle across your lap is all you need to understand the action of the mechanism and the inbuilt mechanical safety. Plus many years experience and depth of knowledge. Then it all just falls into place

Just a question for Peter or others given the age of the weapons is this a common thing I.E does the metal suffer fatigue, is this part of the lock up or for the safety to engage into, it is just a few questions as the bolts cop a bit of pressure spike each time we fire a round. (Just thinking out loud)
As always I appreciate your time in responding to my query.

Age certainly does strange things to steels. It's just the locking logs that take the huge instantaneous explosive pressure load and I have only ever seen a few of them fail - but the long one has never failed so far as I know!

B in O and JM are the metallurgists. That's a degree subject in its own right

From that "other forum" on this same question.
"That's the dohickey that allows the bolt handle to lift without flying open when firing. Might want to be real careful fixing it right."

Welded the bolt and it now cocks ok, I did order a new bare bolt from springfield sporters which I will fit to replace this and keep both bolts with the rifle.

https://www.milsurps.com/images/impo...olt007vi-1.jpg

I would ask you to scrap the defective bolt. The reason being it is safe while in your possession as you know it is a re welded safety stud. However when you die and the rifle goes to auction / gets bought / moved on, who knows it's defective? If it is used and fails not ony does someone get hurt or killed it puts the use of ALL old rifles under scrutiny. Everytime an old rifle fails there are scaremongers trying to bring in new regulations from insisting that they be re submitted to proof every time they are sold to bans on their use on ranges. You have to remember that large numbers of shooters are stupid and many will hear what they want to hear, the debate on DP rifles highlighted that. It is another reason why the 'MAX load / Max velocity' / All powders are much the same' brigade have to be asked to see reason, its not just themselves they put at risk it is the whole historic arms shooting community they put at risk. If we do not act sensibly we will be the last generation allowed to fire these rifles.

I couldn't agree more Robert 303. You are clearly a good welder Jagman - but not a metallurgist. The rear end of that bolt, which le loaded to a proof pressure of a lot, is a complete unknown now

ALL components of ALL Lee Enfields prior to the introduction of the No4 were made of CARBON steels and "Malleable iron" of various types. The specification explictly excludes the use of "alloy" steels unless specifically approved by the folk at the top of the Ordnance tree. I have the recipes for most of these carbon steels and malleable irons, but have NEVER seen the exact recipes for the heat-treatment regimes. "Heat to cherry-red, hold for X minutes and quench in oil" leaves a LOT of room for variable results!! (Sunny or overcast, well-lit or gloomy foundry/workshop, fresh or tired workers, slow day or mad rush.................)

I would suspect that a "performance" spec was set in the contract documentation and then the makers had to "do their own thing" to achieve it. That still happens in a lot of fields today. The difference is that these days we have pyrometers to measure the workpiece temperature fairly precisely and a huge variety of alloy steels that can be made VERY hard and still retain a tough core that is not prone to shattering.

The other thing that is creeping up on EVERY piece of iron-based equipment from the Industrial Revolution onwards, is "age embrittlement". The molecular structure is NOT set in concrete, thus the Carbon in these early materials tends to "move around" and form new structures that tend to increase the brittleness of the components. Furthermore, it didn't much matter what the "recipe" called for, there was pretty much no way of accurately analysing materials until the early twentieth century, and we have come a LONG way since then. Thus, folks should be wary of firing genuine antique muzzle-loaders; the barrel probably won't burst, but forged parts like cocks and frizzens will start to fracture.

Another source of these symptoms which I saw recently, was that a No.4 firing pin had put into a SMLE bolt (de-act, as it happens). Every time you pulled the trigger the pin was driven hard into the bolthead and wedged there, stopping you opening the bolt.
I made a brass collar to go on the front of the pin's collar and stop it moving so far.

Anyone have knowledge or experience of cryogenic stress relief and its value if any in "treating" older firearms or other steel or iron objects?

It's a pity we don't have access to a x-ray spectrograph to analyze the steels used, particularly where there have been failures.