Bolt head sizes?

[amadeus76]

Curious so I know what to look for, what are the corresponding measurements for the different bolt heads for a No.4 rifle?

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[CINDERS]

Its like a bowl full of nuts and bolts there is no real definitive size apart from whats stamped on them I am not sure if it was Bruce in Oz who was doing up a list of bolt head sizes and honestly they are all over the shop at least mine are, No's are 0, 1, 2, 3 there is a 4 but the only known one so far here is held by Brian Dick I think if its getting to the 3 then your receiver may be getting to the service limit or the bolt is one or the t'other......... I will see if I can find the information for you think I have it stored somewhere!

Here ya go found this in my records I think this answers what you asked and what I have just said quite well.

And if you are going to buy any of them you want the largest you can get because you can take metal off but there will be no shimming of a short bolt head, although some shooters have used the dangerous practice of leaving 1 full turn out of the bolt head.
This is incredibly dangerous as the threads on the bolt body and bolt head threads take the strain of firing not the recoil surfaces of the bolt and the bolt head body where it contacts the bolt so anyone doing that needs a slap or you stay 4-5 booths away from them it should never be done, I am sure others will agree on that one.

[Maxwell Smart]

I think it might have been Alan de Enfield who was compiling the bolt-head length list.

Measuring the actual bolthead is the only sure way.

[Sunray]

There's no 100% guarantee that just going up by one bolt head number will fix a bad headspace issue either. It does give you a place to start vs a No. 1 Rifle where you start with a handful of bolt heads.

[MGMike]

If you are unable to close up the headspace acceptably with the bolt heads on hand --and you've examined the receiver locking buttresses and are satisfied the receiver's not damaged from setback-- try a different bolt body. For shooting purposes it won't matter that the number doesn't match.

M

[Peter Laidler]

I think that the real answer to this thread has been answered a zillion times already added to by the brilliant printout by Alan de Enfield shown above.

But changing a bolt body is also a bit of a mysterious art But once again, described here several times for the competent

[Bruce_in_Oz]

Then there are the Australian "coded" bolt-heads for the No1.

There is even an official table of them in ancient EMEIs.

The STANDARD bolt head, one size (allowing for tolerances) fits all.

Thus: From A.I.D. 1318A Sheet 2 of 4:

Overall length (sets the firing pin protrusion) - 1.329” Accept, 1.324” Reject.
Main body length (part of headspace setting) – 0.635” Accept, 0.632” Reject.

HOWEVER, post WW2 Australia introduced a range of longer bolt heads. Viz:

Part Number Body length Size No.
B1/BAA 3425 0.635” 5
B1/BAA 3426 0.636” 6
B1/BAA 3427 0.637” 7
B1/BAA 3428 0.638” 8
B1/BAA 3429 0.639” 9
B1/BAA 3430 0.640” 0

Squeezing the last bit of life from the No1 before the L1A1 took over.

[Maxwell Smart]

Bruce in Oz, I've seen quite a few No 1 boltheads on sale here in recent times, which have an freehand electro-pencilled/engraved "P" underneath them.

Would this have a specific meaning?

[Bruce_in_Oz]

As far as I know, the electo-pencilled markings are an Australian thing, often accompanied by two, roughly drawn crossed pennants. It is a proof mark.

It seems to be found on replacement bolt-heads, because the one in the rifle is essentially "proofed" with the rest of the barreled action at the factory.

I haven't found it, yet, but there is probably a clear set of instructions somewhere.

Interesting note on the Lithgow drawing for the bolt-head, C-643, dated 13January 1921, is as follows:

NOTE! For spares, qualify between 9deg and 13deg in advance of new component. Thus ALL replacement bolt-heads as first issued, have a built-in allowance for the gun-plumber to "fit " it to an already fitted bolt body and/or allow for thread-wear inside that bolt body.

The only marking specified on that 1921 drawing is the letter "M", which is to indicate bolt-heads made from "mild steel" as opposed to the originally specified "malleable cast iron".

Further digging required. I can't be the only keeper of old Lee Enfield tech docs on the planet.

[browningautorifle]

NOTE! For spares, qualify between 9deg and 13deg in advance of new component. Thus ALL replacement bolt-heads as first issued, have a built-in allowance for the gun-plumber to "fit " it to an already fitted bolt body and/or allow for thread-wear inside that bolt body.

I had a #5 that you had to fight the bolt to get the head to rotate enough to remove...suggesting it had never been fitted at all. It would be so tight that you needed a screwdriver to break it loose to lock it down when assembling. Now I get it...