No.4 bolt heads specifications

[bow]

Hi ! i'm planning to build bolt head for enfield No.4: i'm not alone. Two friends of mine are metallurgical engeneers and machinist so we could try... Now i need some data:

-- the threads on bolt heads..what is it?
-- What iron should we use . i red somewhere that bolt heads were manufactured using grade "5" iron. Could we use "6" or "7" ?

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.

[Peter Laidler]

The first question anyone will ask is WHY do you need to remanufacture bolt heads Bow?
The second is this. IF....... and I seriously question this......... IF your friends are matallurgical engineers (or metallurgists but you didn't quite say that.....), then they will EASILY be able to establish EXCACTLY what the material spec of the bolt head is. That is a simpe fact.
Even if they are just simply good engineers, they will EASILY be able to use a shadowgraph - or even a simple steel ruler to establish what the thread form is.
Something just doesn't ring true here. And here's another point to ponder. If you want to make an extended bolt head to, say extend the life of an un-C.H.S.able rifle, then don't bother. The body is worn out/through the induction hardened surface of the locking shoulder

Just my 2c's worth. Any thoughts JM, Bruce from Oz and Son?

[bow]

The first question anyone will ask is WHY

Because i have a No.4 in mint condition made in 1950 at Long Branch arsenal. Bore is 0.302, very tight and good looking. It seems to be the perfect rifle. But...it mounts a "3" bolt head, 0.339" long.. Headspace checked is o.072" so bolt doesn't close fully on a 0.074 gouge , I believe the rifle is safe to shoot but brass has short life. Soldiers do not reload during the war; shooters will do.

I checked bolt tennons using engeneers blue and it is fitted very well, as for your instructions Peter. In conclusion, the rifle is very good... well bedded, good bore. Probably it was wide-headspaced at its birth in 1950 and never touched.

[Alan de Enfield]

But...it mounts a "3" bolt head, 0.339" long.. .

Are you sure ?
Do you mean 0.639" ?

0.639" is not a 'large'size 3 and there are many, many number 2 bolt heads that are 'bigger' than 0.639"

[bow]

Do you mean 0.639" ?

0.639" Alan... i did a mnistake on writing.

---------- Post added at 07:56 PM ---------- Previous post was at 07:53 PM ----------

If you use small rubber/neoprene o-rings at the base of the cartridge for the first firing your brass will never know what the headspace measured. It'll last just as long or longer than can be achieved by any other method

But ith o-ring will reduce headspace first time the brass is shot..but the second time , withouth o-ring , it will be stretched ... What i hadn't understood?

[Maxwell Smart]

But ith o-ring will reduce headspace first time the brass is shot..but the second time , withouth o-ring , it will be stretched ... What i hadn't understood?

The o-ring, in theory, takes up the excess clearance and holds the base of the case back against the bolt face, and allows the neck of the cartridge to fire-form itself forwards to the shape of your chamber.

As V-H says above, for this idea to work, you must then reload using neck-sizing only, so that the shoulder location is unchanged, and at the next firing the case will ,in effect, almost headspace off the shoulder. This will give absolutely minimal stretching of the case, and maximise case life.

If you reload for more than one .303, the downside is that you will likely have to keep brass separate for each rifle, due to the difference in chambers.

[Parashooter]

. . . But ith o-ring will reduce headspace first time the brass is shot..but the second time , withouth o-ring , it will be stretched ... What i hadn't understood?

I suspect what you haven't understood is that the shoulder alone is sufficient to prevent end-play (and consequent stretch). Here's an excerpt from "Headspace 101" focusing on this issue -

. . . If you handload for a .303 with generous headspace, there's no need to mess with bolt heads - changing the rifle's clearances to yield longer case life. You can control head clearance simply by changing technique.

When you fire a new case for the first time, use an improvised spacer ahead of the rim - anything from a precision metal washer to dental floss can work to hold the the cartridge head firmly against the bolt face and eliminate or reduce stretch even if head clearance is significant. Another way of accomplishing the same end is to use a bullet seated out far enough to jam into the lands, "headspacing" on the bullet instead of the case. Such techniques are useful only if the rifle has excess headspace. With normal headspace, initial stretch isn't enough to worry about.



After you've fire-formed your new cases they will fill the chamber fully, stopping on the shoulder just like a rimless cartridge. If you neck size, you'll have zero "headspace". If you have to full length size, adjust the die so the cases chamber with just a bit of resistance in the last few degrees of bolt rotation. . . .

To demonstrate how we can control head clearance using only the shoulder, I filed off the rim of a once-fired Remington .303 case. After adding an extractor groove to fit a Mauser-size shellholder, I neck-sized, reloaded and fired this case 19 more times.



The load was a 180-grain jacketed soft-point over a lightly-compressed charge of IMR 4350 (giving an average velocity of 2310 fps for the 19 shots and listed at just under 39,000 CUP in my IMR data booklet). The test rifle was a 1943 Lithgow S.M.L.E. Mk.III*. 20 shots was enough for a practical test, I sectioned the case to examine the web/body junction area where thinning normally occurs.


This case, fired 19 times with no rim, has not stretched or thinned at all. I'm sure it could have continued for at least another 20 of these moderate loads.

It's clear to me that the .303's shoulder, alone without help from the normal rim, is entirely adequate to maintain "headspace" when sized in a way that preserves the shoulder location. Those handloaders who experience poor case life with neck-sized handloads should look for other factors to explain premature case failures. The most likely source of trouble is high pressure. More pressure means more action flex and that means shorter case life.

[Brian Dick]

Your rifle is fine in my humble opinion. Why fix it if it isn't broken? People can't seem to grasp that bolt heads came in different sizes for one reason and one reason only, production expediency! If a new rifle took a #3 to pass the .074 gauge, then that's what was used. Neck size only your fire formed brass and it'll last twice as long as full length sizing, shoot and enjoy your rifle! I challenge you to fire it enough to need a longer bolt head in your lifetime.

[jmoore]

If you use small rubber/neoprene o-rings at the base of the cartridge for the first firing your brass will never know what the headspace measured. It'll last just as long or longer than can be achieved by any other method.

[Ridolpho]

Thanks Bow for asking a question I've been wanting to ask (ie. why doesn't someone build some new large size bolt heads?) and thanks to everyone else for answering said question! My specific rifle of interest is a 43 Longbranch that had one of the 6 groove barrels installed in the 50's and in very good condition. It headspaces (and shoots) OK but the bolt head measures 0.642 leading me to wonder where I would go from there if I shoot it a bunch and it opens up.

Ridolpho