No.1 Mk3 Bolt Cracks

[Peter Laidler]

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)

[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.

[Homer]

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

[mrclark303]

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?

[mrclark303]

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?

[Peter Laidler]

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.

[David TS]

Peter

Was this it?

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

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

[Peter Laidler]

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

[muffett.2008]

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.

[mrclark303]

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.