Lee Enfield mismatching bolts

[303Guy]

I have one or two Lee Enfields and most of them have mismatching bolts. With all those, it's the outside lug that engages which is also the strongest lug but still. I know that these rifles have been fired with full house loads to no ill effect but in principle, this is not a good idea.

So, what exactly is the ill effects of firing full power loads with only one lug bearing?

Also, what would be considered a safe load with such a rifle?

One rifle I acquired even had a mismatching barrel! It had a Martini 303 barrel on it which was loose and could not screw in all the way due to the extractor alignment. Well, I shot this rifle with low pressure loads and it was accurate with paper patched boolits. I should say that apart from the barrel not screwing fully in, the lug recesses showed a lot of set back. Who would have thought a loose barrel would shoot straight?

By the way, I do have a few guns with matching bolts so there are some shooters in my collection.

[2152hq]

A matching bolt would only tell you that upon mfg, the rifle had headspace that was within spec.
Wether both of the bolt lugs bear against the recv'r or not,,only a check with a marking fluid or carefully smokeing the surfaces one at a time and trying for fit to see if they actually both contact will tell you if they are so.
They may not even both contact if a 'matching numbered' bolt is in the rifle.

It's not uncommon for only one lug to be taking up the full force of the load and the other to be completely lacking contact. Or the other to be just barely making contact.

A mismatched bolt may well have perfectly good contact in the rec'vr as well as any other. The headspace may be off though.
Two different things at work.

The smaller lug and it's seat in the rec'vr can often be simply viewed and seen to be battered and set back from firing. This from the larger outboard side lug not bearing at all in support,,the smaller lug taking all the load and setting back till the larger lug comes in contact.

[Adam Helmer]

I have 30+ SMLEs and some bolts do not match. Since the .303 headspaces on the rim, it is not a big deal in my opinion. When I reload, I do back off the resizing die and load for each specific arm and note which arm on the loading data sheet.

I have a favorite MkIII that NEEDS a back off of 1.5 turns on the sizing die. Most other SMLEs require less and is so noted. Matching numbers do not mean much in my opinion, only resizing die adjustment for a slight "Crunch Fit" is what is needed.

Adam

[Multigunner]

Due to the necessarily stout extractor spring any slack in the fit of bolt body to rear receiver walls will allow the bolt to tilt to the right. Even if both lugs make good contact on firing when under pressure they won't always show it by smoking the lugs if checked with the extractor in place.
What's important is that both make contact with the seats when under pressure.

The slight spreading of receiver walls after many firings adds to this situation. Too much slop would suggest several over pressure firings. Firing in extreme heat can cause this and it was noted on No.5 carbines used in Malaysia. The walls spreading enough that sight pivot locking pins were sometimes sheared through.

I had a Lithgow that showed excessive spread years ago and corrected it by squeezing the walls with a heavy bench vice with bolt in place. That took all the slack out, but I don't trust that receiver with full power loads so I put it aside for a .410 project I've yet to get around to.

[2152hq]

Don't check headspace nor lug seating with any springs assembled in the bolt for the very reason you mention.

It's common, especially to check headspace in bolt rifles to just drop the gauge in and lower the bolt. But to do it properly, any springs and bolt components that may compromise the reading as you point out should be removed, Also the bolt and the lugs cleaned before and reading is attempted.
Since a couple .000 of an inch makes the difference betw good and no-good,,contact and no contact, any tiny amt can effect the reading.

In the Enfield,,take the bolt head right off to check the lug seating.
Mark them, replace the bolt, hold the trigger back to get the sear out of the way and apply some pressure to the front of the bolt body from down the bore as you work the bolt a couple times to show the contact in the seats,,or lack of it.

[303Guy]

Thanks for that. One rifle which had a lot of set-back bore on both lugs. My matching bolt rifles do bear on both lugs, using marking pen ink. I'll recheck with bolt heads removed.