Lee Enfield mk4 No1 Cracked Bolt

I'm going to revise my previous speculation. I think the bolt failed in bending. With the bolt riding on one lug and perhaps a twisted or bent receiver, there would be introduced a beam-style bending moment. The bending moment would exist behind the lug, and would be at close to maximum in that area.
I can see why it is important to keep everything straight, with the loads axial and axisymettrical, in a rear lug design like the LE. The bolt itself, being hollow, has relatively little stiffness in bending.
 
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Andy said:
Nothing is holding the back portion of the bolt (from the break back) in place, so how could how could any rearward force cause that break?
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The left lug broke in two places, the break ahead of the lug seems to have happened first, shearing the bolt, thereby leaving the lug weakened where it immediately and subsequently broke off from the rear. You can still see a small splinter attached to the rear segment of the bolt.
 
You might want to pull down the remaining ammunition in that lot. I wonder if that was caused by screw-up in the production line and the round in question got a double charge.
 
If you haven't already, contact the seller... if it was firearmscanada I'd be suspicious, lots of fudds and ripoffs on there. Someone may have seen that and offloaded it quickly because they realised it was a dud.
 
Ready said:
...... or if anyone else has had this problem.
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As claven2 pointed out, there's an ongoing and very interesting 9 page thread (so far), loaded with pics of all sorts and in some cases, the causes are coverered and discussed with Peter Laidler, who is the senior Armourer in the UK Military, now retired, but based as a Technical Officer at the UK Military Small Arms School.

Even if you're not a technical geek like me, the pics are fascinating and now I remember why I always wear by shooting glasses. ;)

Gallery of Dramas. Broken Enfield Parts! http://www.milsurps.com/showthread.php?t=27425

I know there are No.4 bolt failure pics in the thread, but just didn't have the time to wade through all 9 pages and find them.

Regards,
Doug
 
Winchester-1897 said:
Was it a drill rifle?
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I was wondering that too but it does look like a No4 Mk I action, were No 4s used for DP ? I know many older rifles like SMLEs ended their days as DP rifles.

I'm not sure if I caught this or not but has the rifle been turned into a sporter or is she full military configuration ?
 
Nabs said:
I was wondering that too but it does look like a No4 Mk I action, were No 4s used for DP ? I know many older rifles like SMLEs ended their days as DP rifles.

I'm not sure if I caught this or not but has the rifle been turned into a sporter or is she full military configuration ?
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I sort of wondering what markings the rifle had. Usually drill rifles were clearly marked as such.
 
Very interesting, it looks like they very clearly distinguished DP marked rifles. It looks like they went as far as electro penciling "Drill rifle" on the left receiver wall of No 4s. I wonder if this may be present on the rifle in question ?

The op did mention he fired four shots out his rifle before this happened. We have all seen the result of someone firing one shot out of a DP marked SMLE not too long ago.

To eliminate the DP rifle possibility, we will have to see more pictures of the rifle as a whole, and close ups of the receiver and receiver wall as well as possible shots from the rifle disassembled.

The last thing I want to have happen is for the op to put a replacement bolt in and for the whole rifle to give way.
 
John Sukey said:
You might want to pull down the remaining ammunition in that lot. I wonder if that was caused by screw-up in the production line and the round in question got a double charge.
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When I finally got the discharged round out the primer came completely out of the casing
 
probably cause its british... if it was canadian made it would have never happend... you should buy a .22lr like me, mine never broke the whole day while we where up in the mountain shooting... and it only cost me 5 bucks to go for the whole day... it only cost you 5 bucks also but you only got 4 shots off lol... jk :D

post up that pic of the shell that caused the bolt to break....
 
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here are some pictures of the rifle
 
I've seen this before. That bolt is hard and suppose to be malable. It may have been made too hard and brittle. It probably was dropped on a hard surface, like many would have in the last 3/4 century, and sustained a crack. Eventually torque led to the failure you see now. It's best not to try to save it by welding etc., too dangerous.
I was a reg force weapon tech and personally owned a couple hundred enfields since the 80's, so I have seen a cracked bolts, to a cracked bolt head, bulged and 2 split barrels.
 
John Sukey said:
You might want to pull down the remaining ammunition in that lot. I wonder if that was caused by screw-up in the production line and the round in question got a double charge.
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Ready said:
When I finally got the discharged round out the primer came completely out of the casing
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The primer pocket appears to be enlarged quite a bit, and the only cause for that of which I'm aware is very high pressure - of which there are multiple possible causes. Not too many ammo manufacturers use powders that can be double charged, and I've never heard a reliable account of a commercial ammo manufacturer using the wrong powder, but on rare occassions home reloaders have.

I don't imagine you'll be using that firearm again, but as for the ammo, I wouldn't use it either. As John suggested, it would be interesting to pull down the remaining rounds and weigh the powder charges, as well as watching for any indications that different powders might have been used.
 
The flashhole looks way too big and the primer flattened, a sign of pressure.
A picture of the sides of the case could also help.
To confirm ammo wasn't reloaded, look at the primers on the rest of the ammo from that batch. They should be bronze in colour and slightly rounded as opposed to silver and flatter for reloaded ammo. Yours doesn't look like a reload but it's hard to tell from picture.
 
Claven2 said:
Andy - I think it's an oversized Berdan primed case.
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How do you explain the single centre flash hole then? :p

He did say that the primer "fell out" too.

"Flattened" primers can occur for a host of reasons, many of which are at moderate pressures, but an enlarged primer pocket is a sure sign of high pressure.
 
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