No.1 Mk3 Bolt Cracks

Some time ago I sold a No.1 Mk3 Enfield to a good friend. He shot it a few times without any problems. Yesterday, he told me he was just cycling empty brass through the gun and noticed a hangup on the bolt. When he took it out, there was a crack going completely around the bolt. I have never thought something like this could happen. Does anybody have any idea why or how this is possible? Was it metal fatigue? I am glad that this did not happen while he fired the gun, it could have been very dangerous. Photo shows the crack on the bottom bolt.

Wow! It almost looks like the left lug was carrying all the stress and the tube sheared in response. Do you know if both lugs showed similar signs of wear where they contact the shoulders of the body?

Ridolpho

I have never seen that! A couple of cases of cracks through the left hand side of the action body in front of the charger bridge, but never a bolt cracking.

The forces on it must have been absolutely tremendous.

I'd be curious to know what ammo he was shooting. I have seen that once before. It was a too smart for his own good competition shooter in Florida and a new No.4Mk.2 and a gross over charged handload. The bolt was broken clean in two in about the same spot.

Thank god he noticed before he shot it again!

If the bolts destroyed, I bet the action body stretched to hell too.

I will get more information about this bolt crack later when I see my friend and look at the rifle. He has told me all he has shot so far were 60 cast bullet loads. The No.1 Mk3 is not a matching gun, but the headspace appeared to be tight, no bolt movement when closed on a shell. I got the barreled action as a factory refurb with a new barrel. The bolt was from a different gun.

I am not being a dick but was the bolt correctly fitted to the action as has been stated here many times before by those on this site as trained armourers and gunsmiths of the Lee lineage its not just a case of dropping in another bolt and checking on a go/no go he and yourself were lucky it did not let go under firing conditions even shooting cast bullets there are still 0000's of psi at play right in front of your nose.
This will be an interesting thread for those interested in such doings as its the first one I have seen that has a failure like that, if it was another bolt from a donor gun or just a old 2nd handy then its past is unknown and it may have been ready to fail at any point after it was mated to your rifles action interesting indeed!

Thanks Cinders. I did not know about the bolt fitting procedures. I have given my friend a spare bolt I had and hopefully will try to install it correctly, that is if it is possible at the left lug.

Do not shoot that rifle again!
I strongly suggest that if you or your friend are not skilled and understanding of how the Lee Enfield action locks up (Fitting up the bolt) then you need to find a gunsmith that does, Brian Dick of BDL (His business) who frequents this site is very skilled at fitting them up and checking the rifles over I suggest the outlay in getting it done correctly is cheaper in the long run as you have both had a very narrow squeak.
The nominal operating pressure for the Lee's MkIII & No.4 is @42,000psi and if the bolt lets go the shrapnel is only going to come out one way and thats backwards...........!

Get it fitted up correctly please.

I would strongly concur with Cinders, under no account shoot that rifle until its been fully checked over and declared safe to shoot by a gunsmith.

Perhaps it was a pre existing fault with the bolt ... Perhaps not!

The action body could be fatally compromised by distortion and stretching.

THE ACTION BODY STRETCHING SCENARIO IS A TOTAL MYTH............... I have already put it to bed once on the forum if anyone cares to resurrect the article. Things stretch be being put under tension - as you do with a TENSION spring or putting a bolt under TENSION by tightening it in hole against a nut. I won't go into it again but think about it, whether it's a Bren, L1A1, No1 or 4, the rifle body is always in compression. That's why you get bloody recoil.................. I've got my steel helmet on again, ready to face the wrath of the amateur physicists and metallurgists.

That is where bolts ALWAYS fracture and it is simple metal fatigue* where the bolt is hardened/tempered/toughened across the locking lugs. Looks like an incorrectly fitted bolt or worn body but only metallurgy will show

Calm down dears........
(*not strictly mechanically correct but sufficient for our example)

:) I'm sure I've posted pic's of fractures around the small lug before...................that's my excuse to visit the local aircraft maintenance boys and use the crack testing gear.

Peter did you see this type of failure often in service?

Interesting, never seen a bolt body crack across before, only cracked and fractured action bodies.

Was this more an SMLE thing than a No4 Peter?

So not stretching (getting ready to put on the dunce cap here and face the wall)

Compression damage to the action body from bolt failure, would that be right Peter?

Did I see the failure often in service. No. Once on a bolt taken from a rifle in the 80's. oince on a civvy rifle that Fultons had in their collection and another on a sample bolt set up tio fail by students that was analysed as catastrophic metal fatigue loading. I wouldn't say that it was a No1, 4 or 5 failure. Just a failure across the hardened/toughening part of the bolt - just something to look out for every now and then. The steel won't give you any notice (JMoore ?) there, it'll just go but the bolt will not cause you injury when it does. It won't happen again because you won't be able to re-load!

Good Q Clarkie. But no compression damage to the body because the shock loading of discharge has already passed through the body and on to your shoulder in the form of recoil - and that loading was via the locking shoulders in any case. As I said, there won't be a next shot with that bolt!

Maybe someone wot is compu'a savvy can bring up the article wot I writt about 'stretching' bodies some time ago.

Peter

Was this it?

Was it a post in a thread, or a thread title?

http://www.milsurps.com/showthread.php?t=51064

Nope....., it was a thread that started about stretched No1 bodies that got me ranting............ You'll know it when you read it!!!!!

These are a few that we have discussed here on MilsurpsAttachment 92962Attachment 92963Attachment 92964

I have a few others showing fractures around the small lug and bolt handle root on another computer somewhere.

Just as a matter of interest, I conducted a shear test on the small lug of a DP bolt given to me by Demo(Homer), it sheared at 62.8 tons...........that's a bloody great load on a small appendage, remember the rifle is proofed to 24 tons.........back in the year dot, so fatigue and bad maintenance will figure in pretty well, remember these rifles are not getting the regular inspections and tests they did when they were in service..............and I'm sure no one expected them to be still banging away 100 years + later.

Quote:

---

Originally Posted by muffett.2008

These are a few that we have discussed here on Milsurps

I have a few others showing fractures around the small lug and bolt handle root on another computer somewhere.

Just as a matter of interest, I conducted a shear test on the small lug of a DP bolt given to me by Demo(Homer), it sheared at 62.8 tons...........that's a bloody great load on a small appendage, remember the rifle is proofed to 24 tons.........back in the year dot, so fatigue and bad maintenance will figure in pretty well, remember these rifles are not getting the regular inspections and tests they did when they were in service..............and I'm sure no one expected them to be still banging away 100 years + later.

---

Very interesting, I will certainly keep a close eye on my well worn 1917 SMLE. As you rightly say, no one would have thought in their wildest dreams that these grand old ladies of the battlefield would still be in regular use 100 years on.

Quote:

---

Originally Posted by muffett.2008

:) I'm sure I've posted pic's of fractures around the small lug before...................that's my excuse to visit the local aircraft maintenance boys and use the crack testing gear.

---

As have others here. The granular structure at the breaks in those photos was commented on IIRC. I don't know if that was within the normal range or reflected progressive embrittlement due to stress.

The recoil lug in the body that was in closer contact with the bolt lug would have taken more load than normal obviously. Whether that would cause deformation of the lug in the body I don't know, but are they not surface hardened? Sub-surface deformation? Seems likely that the lugs would already have already "compressed" from prior loading as much as they ever would?

As for bolt "set-back" during proofing I will leave that to the experts to explain as well!

Another virtue of the design seems to be that if the bearing is unequal the worst that can happen is this kind of failure, rather than ejection of the bolt, because no matter what happens, that large recoil lug isn't coming off the bolt body.

Peter, have I understood you correctly?
Do you say that
(a) the Lee Enfield action body never stretches [or at least, never stretches significantly];
and
(b) this is because the forces produced on firing compress rather than stretch the Lee Enfield action?
Rob

Yes, that does not make sense, the bolt will be compressed by the charge, react on the action which will be in tension from the bolt engagement to the breech. Else that bolt is moving rearwards.

The pressure on the bolt is directed on to the lug surfaces at the rear of the receiver. There is no load to stretch the receiver from the barrel to those lugs; just the felt recoil of the rifle moving rearward.

RobD, Post 22, yes. There is nothing for the body to be in tension against. The bullet is travelling up the barrel while the cartridge case is pushing the bolt rearwards. Equal and opposite and all that. I wrote this all up as a paper. Bren, L1A1, they're all the same. As students it was a very simple and easy to see classroom project.

PZKW, cvan't fathom out whether you agree with the laws of physics or disagree. You'll have to elaborate. There's nothing in tension..........., the round is moving forwards, pretty-well frictionless* up the barrel. I even explained this in the original paper too. I wonder if the paper might be in the L1A1/FN thread somewhere when that related to the mythical 'stretching' bodies.
* there is friction oif course but nothing to cause sufficient tension in our lifetimes sufficient to 'stretch' a body!!!!!

What I alluded to with the original OP's dilemma was the spare bolt is not just a drop in fit and away you go, I could swap the bolts on my wifes 308 Barnards and they will work just as well in either that's because Barnards are held to ultra tight tolerances built for precise breeching up by the gunsmith (My G/S is excellent at his craft when he does a barrel its in a locked up workshop so no numpties will annoy him from the shop)
Dropping a random bolt into a random Lee Enfield without the required fitting of the bolt & bolt head up correctly is just asking for trouble or you may just jag it and be as happy as Larry just do not shoot next to me........

Peter's discussion about action body stretching is the FN FAL forum in the thread "FN distruction tests", post #23

Peter, I am still lost here ...
in your original post on the subject which is here: https://www.milsurps.com/showthread.php?t=50730&page=3
You correctly say" Put simply, to stretch something, you need to pull it apart between two fixed points."
Now, I know nothing about the FN/FAL. But to me it seems obvious that when there is an explosion in the L-E breech, the forces are equally+oppositely directed forward [bullet] and rearward [ bolt face]. The bolt transmits these forces to the back of the action through the locking lugs, and hence through the back of the action to the shooter through the stock [recoil].
BUT the sides of the action body in front of the locking lugs and behind the barrel ring are, surely,"being pulled apart" between those fixed points? Or am I missing something? As a thought experiment, if you sawed through the sides of the action directly above the magazine well, and reassembled the rifle, and fired it, it seems to me the rifle would separate into two parts at that point. So, it seems to me that everything behind the locking lugs is compressed on firing - but the action side walls do experience a "stretching" force. [Whereas in a rifle with locking lugs at the front of the bolt, like a Mauser, virtually the whole action is compressed on firing].
Am I completely mistaken here? Indeed I thought there was a special L-E Armourers' bolt-type gauge which could be used to look for the stretching effect - am I bonkers?
Rob

An interesting thread. Of course, if the receiver does not stretch, the bolt must obviously be shortened under compression. Otherwise why do we require bolt heads which progressively need to be lengthened over the rifle's life?

Rob,
I think at first blush I would have felt the same way about it as you. But putting on my engineer cap (my business card folds into one), I find it helpful to think of the path of least resistance. If one were to strap the action right at the barrel threads to the theoretical immovable object, then yes, it probably would deconstruct itself as you suggest.
But as a shooter, we’re not doing that. We’re placing the butt on our shoulder. So what seems more likely, the forged steel stretching or your shoulder moving and absorbing the shock?
Path of least resistance.
Now maybe I’m missing something too but that’s how I see it.

Quote:

---

Originally Posted by rcathey

Rob,
I think at first blush I would have felt the same way about it as you. But putting on my engineer cap (my business card folds into one), I find it helpful to think of the path of least resistance. If one were to strap the action right at the barrel threads to the theoretical immovable object, then yes, it probably would deconstruct itself as you suggest.
But as a shooter, we’re not doing that. We’re placing the butt on our shoulder. So what seems more likely, the forged steel stretching or your shoulder moving and absorbing the shock?
Path of least resistance.
Now maybe I’m missing something too but that’s how I see it.

---

Think about the few milliseconds after firing- the pressure in the chamber is already several thousand psi but the bullet hasn't begun to move forward and the rifle is not recoiling. As an exercise in "statics" (I can almost remember Eng. 201), with the case head bearing upon the (nicely headspaced) bolt, how can the action body not be in tension? When the Turks wanted to shoot 8X57 from the SMLE why did they weld a bar of steel onto the right body? When the Soviets developed the rear-locking SVT 40, why did they progressively thicken the two siderails of the body? According to Soviet documents, they found body stretch affected headspacing (call it dynamic headspacing as opposed to static). I'm probably missing something here but I went on to be a geologist as opposed to an engineer so.......................

Ridolpho

We're back to 6th form physics classes now where you MUST accept the laws of physics and stop thinking fuzzy logic.......... Or we go off into megga mission creep. Accept that the explosion DOES act all around up, down, round, back and forwards for a megga millisecond and then dislodges the bullet which travels up the bore. The bolt is held firmly against the locking shoulders whence the loading, in the form of recoil is transmitted rearwards in the form of felt recoil. So far, so good. Simple question. Where is the opposing action that will cause the body to stretch when it is already under compression? Stretching in mech engineering terms is when the material has exceeded the bounds of its elasticity and retains that form....... It's stretched! As would a bolt between two girders. Tighten up the nut to 80ft/lbs. Exceed that and the bolt will stretch or exceed the bounds or limits of its elasticity. Simple test at uni to test tensile bolts, try to run the nut down the bolt shaft and it won't run because the bolt had stretched. We know the reason. No such reason for a rifle body to stretch.

Forget broken bolts, this is nothing to do with that (well, it is but distantly related)

Peter, many thanks for your explanation, which for one without an engineering background is most enlightening. However, there is still one thing that I don't understand. If there is no stretch to the receiver, what causes an increase in head space?

just throwing this in to muddy the waters. So I read the action wont stretch because the shoulder takes the recoil. Now with the shooter using the lead sled where will the recoil go? since its not absorbed by the led sled but just held with brute force will that now cause the recoil to be absorbed by the locking lugs?

to the OP was your friend using a shooting aid like the led sled?

Quote:

---

Originally Posted by Mr E

Now with the shooter using the lead sled where will the recoil go?

---

Into the lead sled. That's what they're for...

No engineer here either but my cave-man thinking makes me believe the opposing reaction is transmitted back to the barrel in a radial fashion through the breeching mechanism and how well the barrel is fit to the action face. The vibration is expended into a node. The mass and tension of the receiver to the stock further control the release of energy and keep it true to form. The receiver (body) and well fitted bolt are heavier than the bullet as it travels through the barrel. The kick or recoil is just what happens as the gas exits the muzzle and it's in a straight line which the system can easily overcome because its rapidly decreasing. The energy from the powder burning and expanding is moving outwards in all directions like straight pins stuck in a tomato.
Head space is controlled by correctly heat treated parts that are fitted properly which can repeatedly with stand or overcome cartridge tension to the chamber walls. The cartridge fit I think does all the real work as long as there's something there to keep it in place for a short period of time.

Dunce cap on :yikes:

A snippet from Physics of Guns;

"When one object exerts a force on a second object for a certain amount of time, the second object exerts an equal but oppositely directed force on the first object for exactly the same amount of time. The momentum lost by the first object is exactly equal to the momentum gained by the second object. Momentum is transferred from the first object to the second object. In this case, if a gun exerts a force on a bullet when firing it forward then the bullet will exert an equal force in the opposite direction on the gun causing it to move backwards or recoil. Although the action and reaction forces are equal in size the effect on the gun and the bullet are not the same since the mass of the gun is far greater than the mass of the bullet. The acceleration of the bullet while moving along the gun barrel would be much greater than the acceleration of the gun (acceleration= force mass)."


So the steel would be opposing the forces applied to it equally in the opposite direction I guess.

If one of the armourers or Ginsmiths (typo but it made me laugh) here would answer if my reply has merit in that the Lee bolts are not a drop in fit and to do that without proper fitment into the action is playing with fire as it is not set up for the correct transference of the recoil wave correctly on firing. TIA for your reply.

This is an interesting topic- thinking about it today while casting Snider bullets and managed to burn my hand! There's lots of literature on the subject but I can't find anything that demonstrates that the compressive stresses on the receiver (due to the peak force acting on the gun during recoil) are enough to fully offset the tensile stresses on the receiver (due to "bolt thrust"). Easy enough to guesstimate the possible forces due to bolt thrust (chamber pressure and area of cartridge head are known although pressure reduction due to strength of the brass is uncertain). There are reports of experiments made to try to determine peak recoil force which suggest something in the 500lbf range (applied very briefly, of course). Isn't that going to be a lot smaller than the force due to bolt thrust?

Ridolpho

I know the answer to all of the amateur metallurgists, chemists, gunsmiths and would be Armourers. Just ask yourselves this simple question. To stretch a piece of elastic, you pull it between your fingers. To stretch a piece of leather, you wet it and pull it out on a table. To test a piece of steel to test for shear strength, you pull it (stretch don't forget) between two clamps to stretch it until it shears. Pray, tell me how you stretch a rifle or bren gun body by doing NONE of these stretchy or tensioning type exercises? Nope........, me neither!

You see, I'm a simple engineer. I'm biased in favour of gravity, the existence of the moon and the tides, the laws of physics and not standing in the path of oncoming trains.

Quote:

---

Originally Posted by Peter Laidler

You see, I'm a simple engineer. I'm biased in favour of gravity, the existence of the moon and the tides, the laws of physics and not standing in the path of oncoming trains.

---

:beerchug:

Just trying to absorb some of the debate going on here. First, I have not yet seen the gun but I do suspect that the left lug was not in contact with it's recess and developed the crack while being fired, and then broke in half while being turned at a later time. The owner of the gun has read bolt fitting procedures here and on the Enfield forum and is capable of doing the work himself. He'll be installing a new bolt body which is available from Springfield Sporters, and also check headspace.
My take on forces involved during firing of the Enfield is that most forces generated behind the bullet leaving the gun is simply directed backwards. There is a relatively small pulling force caused by the friction of the bore and bullet with respect to the action. There might be other things to consider when destruction occurs, such as vibrations, metal bounce, etc..