Fitting a new bolt head (different question)

[logandiana]

My #1 bolt had works just fine. I don't know anything about head spacing or the like, but in the short time I've owned it the rifle shoots fine with no problems. The bolt moves smoothly through the action.
This issue is the bolt head looks terribly beat up and it's got a bunch of scratches and dings almost as if it's been dropped on the concrete time after time. It almost has an etched look to it to in some places.
I bought a replacement #1 bolt head simply for looks, but the new bolt head doesn't fit the bolt body. I am now assuming that not only are there different sized bolt heads (0,1,2 etc) but also different sizes amongst the individual bolt head sizes.
The new #1 bolt head is identical to the old one, but the threads must not be aligned the same.
The original bolt head will screw on and will stop about 5 degrees past lining up with the rib on the bolt body. I have heard that this is reasonably within spec.
The new bolt head will screw on but will stop and tighten about 10 degrees before the rib on the bolt body.
As you can imagine the bolt will not fit in the receiver this way if the bolt body and head cannot line up.
It looks as though I would have to remove material from either the bolt body or the back of the bolt head for this to work. Neither of which I want to do.
Were there individual 'sub' sizes of the bolt heads?

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.

[Ridolpho]

logandiana: Some time ago someone on the forum presented a spreadsheet summarizing the range of observed measured sizes for each of the "standard" bolt head numbers. The range within each is large and there is overlap. Your ideal solution is to find a Lee Enfield specialist with a drawer full of bolt heads from which he could probably find a suitable replacement for you. It's not practical to buy a couple of bolt heads hoping for a fit. As to whether or not you should do anything to try to induce your replacement to fit I'll leave it to the expert armourers to comment.

Ridolpho

[Beerhunter]

Even if it is a bit scruffy I reckon that the "If it ain't broke, don't fix it" maxim applies here. Or put another way: "Always keep a-hold on nurse, for fear of finding something worse."

[Alan de Enfield]

I guess you are talking about 'underturn' - the 'problem' is that if the threads start in a fractionally different place then you get either under or overturn, There is a special tool to try to "overtighten" bolt heads for a No1 rifle but I've not seen one for the No4 rifles.

There is a huge difference in actual 'size' of the same numbered bolt heads - to ensure you keep the same headspace you need to take a caliper / micrometer and measure the distance from the front face of the bolt head to the rear face, measure that in 3 places (120 degrees apart) to get the average. Then compare this to your 'new bolt head'.

As you have found out apart from headspacing you need to consider 'clocking' as well.

Here is a link to the information / spreadsheet I made some time ago. As you can see there is a 0.015" (15 thou) range of sizes all within 'size 1' Lets say (for worst case) that your current bolt head is size 1 & measures 0.637", and gives you an acceptable headspace of 0.070". The new bolt head (still a size 1) measure 0.622" therefore your headspace is now way, way out of specification at 0.085".

Headspacing and changing bolt heads affects all sorts of other parts in the 'trigger group' - its not like changing a wheel on your car, "bolt it on and it fits". If you dont understand the implications of what you are doing, let an Enfield armourer do it for you.

If you have no existing problems apart from visual - leave it alone.

No4 Bolt Head Survey and Instructions

[logandiana]

That's exactly it, the threads just start in a slightly different place causing the 'underturn' as you call it. I'll check it with a micrometer just to see, but I didn't think it would be such an issue to swap it out. I'll just return the new bolt head and it is just a cosmetic issue so i'll just live with it.

[Peter Laidler]

Leave the old on on it. If you insist on a new one/replacement. let someone who knows what he's doing so it......, PLEASE! The er is more to a 'simple' bolt head change than meets the eye. believe me. Just my opinion of course......