SMLE bolt/receiver modification

[tbonesmith]

Hi all, I bought a few No1 MKIII* sporters and range rifles for projects and parts, and one of the range rifles(heavy barrel Lithgow mkIII* 1942) has a small amount ground off the receiver, where the bolt handle sits in the closed position. It appears to be in order that the bolt closes with the bolt handle a few thou past its standard position.
Any ideas on the why, or anyone else seen this modification before?
I'll post pics this afternoon

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Edward Horton]

Questions

1. When the bolt is fully closed is there an air gap between the bolt handle and the receiver ring?

2. What is the head space set at?

3. What is the bolt head length?

On a No.4 Enfield with a No.1 or No.2 bolt head fitted there must be a given distance (air gap) between the bolt handle and receiver ring for proper bolt operation. With a No.3 bolt head fitted, bolt over rotation becomes a problem. Mr. Laidler covers this in one of his articles and it is explained much beter than I could.

I assume on a No.1 Enfield the same type rules apply but I'm only guessing.

Below is what the manuals states:

[Alan de Enfield]

Extract of relevant part of Peter's notes on CHS :

The mechanics of CHS for the No1 rifle is a little different. The same criteria applies but this time the last EMER dated 1956 for the No1 rifle simply states that the bolt should close over the GO .064” gauge and should not close over the .074” NO-GO gauge. Sounds simple enough to me! From this I always use the No4 rifle criteria of;
THERE MUST BE RESISTANCE OF THE BOLT ONTO THE .074” GAUGE PRIOR TO THERE BEING A MINIMUM OF .050” FROM THE UNDERSIDE OF THE BOLT LEVER TO THE (its) CONTACTING POINT OF THE BODY SOCKET. So if your bolt starts to resist at .056” or so from its contacting point of the rifle body socket, then if that’s good enough for the Army, it’s good enough for me and hopefully you!
There has been talk of some bolts being ‘ground away’ on the underside of the lever. Quite why is a mystery and my older mentors are unsure why because what will eventually prevent the bolt rotating is the long cam contacting the body side as it’s locked down to the right!

[Son]

The bolt can't rotate any further than the rib on the bolt body will allow- also the other locking lug has a defined end of rotation within the receiver too. besides... Do the math... work out from threads per inch to give how many thou one revolution of the bolthead moves... divide that by 360 (degrees in that revolution) and multiply by the degrees of overturn to give a gain in thousandths of an inch. I assure you, it ain't gonna be big!
Besides, the last few thou past the proper finishing point only take up the play in the thread- The contacting surfaces are already able to be together, (but unless the action is cocked, held apart by the striker collar contacting the back of the bolthead) meaning there is no gain anyway.

The only logic I can think of is it's bubba's attempt at stopping the bolt handle lifting when dry firing by supposedly getting it off the tapered surfaces of the locking lugs... and it cannot do that without grinding a heap of other bits as well.

[Bruce_in_Oz]

I have never seen any official reference for this practice of grinding the bolt knob or receiver. Replacing the bolt body would be correct military practice. However, when you do not have an Ordnance system behind you, improvisation sometimes occurs.

A few days ago there was some discussion about bolt handle "flip" during dry and live firing.

Some of this can be attributed to striker spring torque. There seem to be several other factors.

Some of these are (may be):

Lee-Enfields have helical breech locking (1: 0.1" helix)
When the bolt is cocked, the striker is pulling the bolt lugs backwards against the helically cut shoulders.

When the striker is released, it is stopped suddenly when its collar strikes the rear of the bolt-head. This causes the entire bolt assembly to jump forward; moreso on an empty chamber. It will then rebound against this helix and thus be tempted to twist.

I have noticed that rifles with "bolt handle "flip"" tend to be generally a little "looser" than a new example.

When the action is fully closed, The bolt knob should not touch the side of the butt socket.

If the knob of the bolt handle is in contact with the butt socket, you can almost guarantee that it will flip to some degree when the striker is released. Bear in mind that the bolt body is not given a lot of lateral support by the receiver; bugger-all in fact. When the striker is released on an empty chamber, the bolt assembly will dance around in the receiver. The looser the fit, the more lively it gets.

Dig out your trusty early SMLE's etc and have a look at the bolthead and striker. The early pattern rifles had a striker with a lug that aligned with a notch in the bolthead to ensure the bolt was not misaligned (partially unlocked) at the moment of firing. The safety studs on the cocking piece and bolt body have a similar function.

Note also that Mauser 98's have an analogous system built into their striker and bolt body for exactly the same reason. The big slots on the bottom of the bolt body are not just to let gas out, but to allow milling cutters in to cut the slot that aligns with the "wedge" on the front of the striker collar.

[Peter Laidler]

It's fair to say at this point that there is no heavenly reason at all why a bolt lever should be or even needs to be ground away on the underside. But if it is, it's not important to the structure of the bolt. But you cannot 'over lock' the bolt. Once the stud on the cocking piece is aligned with the long cam groove in the bolt, it's locked!

[tbonesmith]

After reading all your comments and having had a look again at the bolt and receiver, it seems as though, as suggested, this has been done to allow the bolt to rotate so that in the closed position the reinforcing rib on the bolt contacts the receiver ways/slot/bit under which the mag cutoff is fitted on mkiii's(anyone help me out with the terminology?).
I take it from Peters' comments that the rifle is not a basket case, so I'll clean it up, repair some wood work, and give it a run.
Thanks

ps also as suggested, this has elimated the bolt handle"flip" on dry firing for what it's worth