Lee Enfield mismatched bolts

[Son]

Off_Winters... your mate's problem with cases splitting from the shoulder forward is because the brass is too brittle. There has been some milisurp ammo more noted for this than others, but generally it is a storage problem over a long period. I have some cases here that have split the same way and the projectiles fell out without it having ever been near a rifle.
With the "generous" dimensions of an Enfield chamber, it will "work" the brass a lot on firing. They were never designed to be kind to the cases so they could be re-loaded. Compare the length at the shoulder of a fired case to a new one of the same lot. You'll see what I mean. When you realise how far the shoulder gets blown forward, you'll understand why a couple of thou headspace isn't the cause for damaged cases.

As tiriaq suggested, treat yourself to some new commercial ammo and check out the cases.



I cannot understand the rabid fascination everybody has with headspace. It isn't going to blow up if it is a bit out of spec. It isn't going to destroy your cases if it is a bit out of spec. And to look at fired cases for bulges to indicate headspace problems- ! With the taper of a Lee Enfield chamber, it would need to be 1/4" out of spec to show a visible bulge. What you are seeing is the thin part of the case (just beyond the solid section of the base) expanding to the chamber wall. It may be very slightly larger than the solid part, and will probably show "stretch marks" at this point. This is normal. If the case fails around this line (case head seperation- it WILL happen after enough reloads, but shouldn't with new brass) the brass may be brittle or perhaps the chamber is oversize in diameter- maybe the previous owner polished out some pitting....

Smoothbore, the problem with a miss-matched bolt isn't headspace- headspace can be fixed with a change of bolthead. The problem could be equal pressure on the lugs. On assembly, the bolt body was lapped to the receiver to ensure equal presure on the lugs. Then a bolthead was fitted and adjusted for headspace. Then a proof round was fired- this ensured the rifle wouldn't blow up, but also seated the lugs with the over-pressure recoil. It was then re-checked for headspace, adjusted if needed and sent out.

A missmatched bolt may have only one lug in contact. If so, it will pound that lug with all the pressure untill it allows the other lug to come in contact. This may cause excessive headspace (which isn't a life-ending drama) in a shorter period of time. In extreme cases, if the small lug is in contact, it could shear off. I have only seen one such bolt, and it looked as if the other lug had been ground back. I would suggest you go ahead and use it, but check the lugs periodically. If you are concerned, mark the lug surfaces with a texta, and cycle the bolt a few times to see if the ink is polished off....


In service the rifles were gauged every 5000 rounds or so, with the view to changing the bolthead every 10,000 IF it was needed.

Here's a pic showing a fired case next to a new case from the same lot and a set of headspace gauges. Note the fired case is visibly longer at the neck and shoulder. This is because on firing it has expanded outward and forward to the chamber walls. Look closely- there is a feint line about 1/4" forward of the rim. This is where the stretching begins, and this is where the case will fail eventually after many re-loads. It is not a sign of excessive headspace.

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