About those "stretchy" Lee Enfields

[Bruce_in_Oz]

Consider the US Krag:

ONE, (count 'em) actual locking lug.

A seriously cut-away action body.

A cartridge of similar construction and performance to the .303.

Were they prone to rupture, distortion or detonation in their service life?

So, extending the agony of the "Lee Enfield stretch" caper, I offer the following.

The body of your basic L E is seriously solid on the left side and somewhat more skimpy on the right.

The bolt, on the other hand has a massive "reinforcing' lug on the right side and a tiny one on the left.

The right side bearing shoulder on the right is a substantial lump of metal; on the left it is a tiny nub of steel in a milled-out pocket that can, at MAX offer about 2mm square of contact surface, on a good day.

The bolt body is essentially a thin-walled tube with that long lug integrally formed on the RHS. In "compression" as experienced in firing, the side with the big reinforcing lug will display less elastic deformation than the "plain" side.

This brings us to the No4 and the "lightening slot" in the long RHS bolt lug. Getting into voodoo hypotheses here, but could it be that the "lightening" cut was not just to save a few grammes of steel, but to partially "equalize" the elastic deformation in compression of the bolt body, thus reducing the lateral flex?

The "long" lug is long, not for a massive added margin in resisting recoil, but because all that forward length is there to stabilize the bolt (preventing rotation) as it is fully retracted during cycling. This is somewhat simpler than the lug guides in a Mauser body and more robust than a simple stud 'n' bolt-groove system as seen in several designs like the Remington 788.

Information

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[Havenot]

One thing the Krag does have in it's favor is a large chunk of steel for a receiver.....US Krags have a handle lug as well...they are what they are.....an ancient weapons system in several chamberings . Good serviceable arms in US service. the variations of the US Krag are numerous.....replaced in service by variations of the US M1903...The Krag rifle has lived on as a rather successful sporting rifle and caliber

[gc1054]

Bruce,
As we know there were issues with the Krag bolts with cracked locking lugs when the USG upped the 30 Army service load for higher MV (>2000fps IIRC vs the standard 1940fps). Perhaps just a case of a lack of checking versus design specs/limits (but in the spirit of today's HALT -type testing it pointed out an issue or limit albeit not by intent!).
Not seen any info on related Krag receiver issues.

Wrt the Enfield receivers & the extendo/stretcho scenario, what wore out the bodies per Peter's comments on bolt heads? Simply thousands of bolt cycles with frictional wear and possibly lack of hardness on the rear locking surfaces in the body (again per PL notes)? Or is the "setback effect" in play too and progressive (think L1A1 locking shoulders & initial headspacing setup where setback gets accounted for)?

gc1054