Thread: No 1 Mk III bolt heads
Retrieved: 06/19/2014
So, I've searched through and found a lot of discussion about marks on No4 bolt heads, but I didn't see anything on No1s. If I'm mistaken, I'm happy to have my thread redirected.
The bolt in my LSA No1 MkIII is stamped on the top of the lug with the letter "M" and on the rear face of the lug with the letter "K," while the extractor spring is stamped "3." There also appears to be another proof on the right face of the lug (if the bolt head is rotated so the lug is at 12:00) which has been struck through with an "x."
Any ideas as to what these mean? if it is of any relevance the bolt head measures .635"
bonnieandclyde
Dec 27, 2010
The "M" is the type of iron used, of course I cannot remember what type that would be.
The "X"or "K" may be part of the British bolt proofing mark witch is supposed to be two crossed flags.
The "3" might be a "E",? a common mark on Enfield produced parts.
I do not think the markings have any relevance to the measurement of the bolt head.
armouredbear
Dec 27, 2010
The k and the 3 are very clearly struck and don't look like the ordnance flags on other proof marks. I thought the x might be that but it appears to be struck over something else. Did they not start numbering them for size until the No4?
bonnieandclyde
Dec 27, 2010
No.1 MKIII bolt heads where not numbered for size.
No.4 Bolt heads where, but don't rely 100% on the numbers.
A decent caliper gauge will help if needed in determining a correct size.
SavageShooter
Dec 28, 2010
The M stands for Maleable Cast Iron, also called Mild Steel in British metalurgy nomenclature. It's a very low carbon white cast iron also called No.32 Gun Iron.
This form of iron has extreme resistence to compression. Its case hardened for extra surface strength and wear resistence.
An unusual feature is the surface of the threaded shank holds lubricants better than regular steel would have.
An unissued SMLE bolthead never fitted to an action before would be at the maximum length, and stamped with a small s.
I suppose once fitted the s would be removed, perhaps struck over.
I have a bolthead which has the small s, but its not in the spot I had read that it should be.
Crossed pennants might look like an X.
Markings stamped over other markings are fairly common, and can confuse things a bit.
rdm1962
Dec 28, 2010
I have been wondering about this myself. I have seen "U" stamped on a #1 MKIII bolthead befor. Thinking that it had more headspace I didn't look any further. Is there a way to tell if the bolthead is longer? I guess headspace gauges are the final word but it would be nice to know if the chamber is played out or not.
Alan De Enfield
Dec 28, 2010
rdm1962 wrote:
I have been wondering about this myself. I have seen "U" stamped on a #1
MKIII bolthead befor. Thinking that it had more headspace I didn't look any
further. Is there a way to tell if the bolthead is longer? I guess headspace
gauges are the final word but it would be nice to know if the chamber is
played out or not.
Measuring a bolt head wont tell you if a chamber is 'played out'.
It will only tell you that (assuming it headspaces correctly) that is the size needed to compensate for the bolt body compression or locking lugs compression.
Or you could just read this thread:
And try and sort the good advice from the 'other' advice.
MVolkJ
Jan 04, 2011
If I recall correctly, U and M on bolt heads means exactly the same thing - malleable iron used in construction. Perhaps the two different markings indicates a difference in the spec, or the marking changed over time (though I believe I have seen both M and U on WWI-era bolt heads), or different markings were used by different makers.
Alan De Enfield
Jan 04, 2011
> PICTURE 404
Yes it does look odd - the firing pin protruding is not a problem (it depends
which slot the cocking piece is in). The problem is the damage / pitting
around the firing pin hole.
Maybe the firing pin has a sharp end and has been piercing primers allowing the gas to 'pit' the bolt head face.
The face of the bolt head should be mirror smooth (and clean) - you will occasionally see a ring around the firing pin hole (the same size as a primer) If this is very faint - no problem, but if it is quite pronounced get another one.
If that's the one you are looking to buy - don't.
If that's the one you've got - replace it.
Just as an aside you should be aware there are two types of bolt heads.
a) Has a slot cut into the threaded portion
b) Has no slot cut into the threaded portion
They are not interchangable (don't ask me how I know!)
Additional_Bob
Jan 04, 2011
armouredbear wrote:
is it just me or does this bolt face look odd? perhaps as if the firing pin
is protruding?
It does look like the firing pin is protruding (that's not a trick of the
camera, right?) and there looks to be some chipping around the edge too.
Personally I'd keep looking.
Rapidrob
Jan 04, 2011
I have a box of these bolt heads and other than the marks that have been stated all ready, you do have to measure them to see what you have. I just use a fine tipped Sharpie and write what they measure. If you can find what you need let me know, I may have one.
Alan De Enfield
Jan 04, 2011
Almost forgot - you need to make sure that the bolt head 'clocks' correctly (so it aligns with the locking lug)
If it overclocks then when the bolt is in place the bolt head will have 'unscrewed' slightly. this allows the threads to take the recoil impact, they will get damaged and will increase your headspace as they get compressed.
So - four things to consider :
1) Bolt head condition
2) Size of bolt head (headspace)
3) Overturn (clocking)
4) Slot in bolt head thread.
You will not know if it 'clocks' or not without trying it in your actual bolt.
Recommendation - find a dealer with an assortment of bolt heads, take your rifle (with your headspace gauges) and work thru' his stock until you find one that meets the above criteria.
Its not easy is it ?
Why do you think Armourers went thru years of apprenticship before they were allowed to actually work unsupervised on a firearm.
SavageShooter
Jan 04, 2011
I have one of the slotted, or scalloped, shank bolt heads.
Story on these is that they were part of an earlier design which allowed the user to unscrew the firing pin using the bolthead as a wench. The firing pins for this design had a lug that fitted into the scallop cut.
The threads or diameter seem to be off on the scalloped bolthead. They don't screw into an unworn bolt body easily, but if a bolt body has worn threads the scalloped bolthead can be used and screws down tight.
It seems to wear the threads of the bolt unevenly though, and makes use of a regular bolthead in the same bolt problematic.
Alan De Enfield
Jan 04, 2011
Armouredbear :-Just as a matter of interest (now you've had all the 'what to look for info') why do you want a new bolt head ?
5Batt
Jan 04, 2011
What the others have said, plus:
When fitting a new bolthead, be sure to check the firing pin protrusion & check the cocking piece does not come into contact with the rear of the bolt body in the fired position.
armouredbear
Jan 26, 2011
Sorry it's taken me so long to get back to this. we checked the headspace with a set of gauges and the bolt will close on all of them. When measured the bolt head seems to be slightly lopsided, but the lengths are between (if we are measuring correctly - and if I am remembering correctly - I'm not with the rifle at the moment) .640 and .636. so, I'm starting to wonder if the problem isn't the bolt body (instead? as well?) - maybe the locking lugs have been compressed or the face filed down? I'm not sure what those measurements are supposed to be. that said, I think we'd like to have a good enfield experienced gunsmith check it out. Does anyone know of anyone in the general Arkansas area who might be able to do good service to this old warhorse? My folks travel to Dallas pretty regularly, so that's even a possibility.
SavageShooter
Jan 26, 2011
If the bolt head is actually lopsided, and its very easy to get a false measurement, then it may have been that way since first fitted. These were afterall hand fitted by sanding an oversized BH till they got the headspace they wanted.
Changing bolt bodies won't rectify a lopsided BH situation.
I'm not entirely against replacing a bolt body if called for, I replaced the bolt body of my 1915 which appears to have had a new body fitted before. Only reason I installed a new body was the threads had been worn by a non standard SMLE Mk1 bolt head, these apparently don't have exactly the same threads and some taper to the shank.
Springfield Sporters has unissued BSA manufacture replacement bolt bodies, no serial number but a batch number where the PAA number would be on an original bolt handle at the underside of the root.
The replacement bolts require careful fitting. They are proof marked so they've apparently been proofed before packing away using a sacrifical reciever. A rather battered one by the rough appearance of the unstoned lug surfaces.
Since the LSA is a fairly rare item, and if the bolt is numbered to the action body, I'd only consider a new bolt body as a last resort.
It was expected that the bolts and/or boltheads would require replacement sooner or later.
I suspect the major cause of damage to SMLE and No.4 Bolt assemblies was use of MG ammo which had a higher variation in maximum deviation than the standard rifle ammunition. Some MG ammo fell well within the 45,400 CUP of the MkVII ammunition, but there are reports of much of the wartime production Mk8z generating 60,000 CUP and greatly exceeding velocity specificatons. Ammo like that could loosen up or wreck an SMLE in short order.
I vaguely remember reading of one British manufacturer delivering a huge amount of Mk8z that was found to be greatly overloaded and condemed but somehow finding its way to the front anyway and causing some damage to MGs. Velocity was just under 3,000 FPS, pretty much in the Magnum class. I doubt many SMLE rifles could handle such a hot load.
A very real problem was that ammo within safe specs for use in Europe could generate much higher pressures when used in the 120+ F of dessert and tropical fightng. Sporting ammunition manufacturers, after several blow ups, downloaded ammo destined for India and Africa for this reason.
An Australian warning posted on a Finn site told of Eastern European manufacture Mk8z equivalent ammo damaging rifles there some years back.
I can't caution too strongly against use of ammo not known to be within SAAMI limits.
armouredbear
Mar 07, 2011
OK, so a little thread necromancy here. so we bought this bolt, this bolt, and these bolt heads off of gunbroker (which arrived amazingly fast - so if you are the guys I bought these from, thanks!).
The bolt heads do not match the original bolt - my stupidity, I forgot about the scalloped bolt heads. The super shiny unissued looking bolt fits perfectly and headspaces perfectly, both with the head it came with and at least one of the replacements. The older bolt does not seat correctly, and the head in it, which is the scalloped kind, does not seat easily in the original bolt, which may be due to thread damage on one or the other or some other factor (forgive my vagueness, but I'm doing this long distance - my dad is caretaking my Enfield at the moment). regardless, given that this rifle is a mostly matching (the sight leaf is not matching) LSA, I'm going to keep the original bolt.
so, my question is, what should I be looking out for with the replacement bolt? Are there any safety issues, small or large, to which I should be paying attention? the bolt is not marked "DP" or any other suspicious voodoo, but i want to make sure that we're approaching this in the safest possible way. I am assuming (and please, for the love of God, correct me if I'm wrong) that I shouldn't be worried that I am actually looking at a No4 bolt (which would have a groove in the long locking lug - right?) and which wouldn't fit in a No1 anyway - right?
I appreciate all of the help you guys have offered. thanks.
shoggoth80
Tue Mar 08, 2011
I recall reading that bolt head overclock was acceptable to no more than 20 degrees if my memory serves. Almost all of my Enfield bolt heads overclock a little bit, though they all seem to lock back against the bolt body nice and solid when the chamber is closed.
In my Stratton book, it details the U mark on the bolt head as a "difference in specification." Nothing more. The book doesn't even address the M stamping on the bolt heads. In fact, the only Enfields that I have which show such stampings are a 1940 Lithgow with an M marked bolt head, and a 1916 BSA with a U marked one. They could mean something similar in terms of being white iron. However, I do not have the academic sources to support it, hence my own curiosity on the subject.
I was under the impression that there were two types of bolt head stems... one slotted, and one non-slotted, and that was related to the type of striker used... the later variants being the non-slotted bolt heads. Other than that, I cannot think of a good case for non-compatibility. Though it does stand to mention that I have a late, LATE model RFI No.1 Mk.3* and the bolt head threads seem to be a much coarser style than my other SMLE rifles. Funny enough, this bolt head overclocks the most yet when the bolt is closed it's tight as can be, and appears to bear on the bolt head and bold body, as opposed to the threads supporting any recoil/pressure. Just a side note that I think the game changes with the really late model No.I rifles.
Dunno if this lends you any insight armouredbear. Apologies if it just seems like useless filler.
Edit: On visual inspection, the threads between the late RFI, and the others does not appear to be any coarser than the others. It just feels like it when installing the bolt head... like I get more travel per turn. Nothing wrong with them though, as I compulsively went and did a quick visual on them all. Funny enough, my oldest rifle has the least over-turn.
armouredbear
Mar 09, 2011
It's all very helpful, thanks. I guess my only remaining question is regarding the safety procedures surrounding replacing the bolt and if there are any compatibility concerns that I should be aware of before we test fire. Everything I've read suggests no, but i wanted to check with the experts around here to make sure.
shoggoth80
Mar 09, 2011
Well, I know some of the more experienced folk know how to smoke the lugs to check for even/proper bearing. I know what the process checks for, but nothing on how to do it.
If you haven't searched it yet, toss that into the search function. If you cannot find answers you need, I'd say post a new thread asking what/how to do it. I'm not a gunsmith, nor claim to have much experience doing "gunsmithy" things. I'm just an enthusiastic amateur. Haven't had to worry about bolt heads and headspace. When it becomes necessary, or when I am not occupied with other tasks, I might look into it more.
Alan De Enfield
Mar 09, 2011
Some years ago Peter Laidler wrote a series of 'how to', fitting a new bolt in an Enfield is fairly complex and is written in three parts - here is part one for your consideration (the next two parts cover correctly installing the striker, the striker spring and the cocking piece)
The notes talk about a No4 but a No1 is the same.
Fitting a Bolt[i]"First things first. Bolts could only be fitted at Field and Base workshops because they were the only ones that had a 'GAUGE, Inspectors, Bolt'. This is a brand new, calibrated bolt. Still in white metal and marked as such. If my memory serves me right, the slot in the long/top locking lug is machined right through to identify it. So that's the reason if you have ever seen one. This bolt is bare. Clean the locking lug surfaces of the rifle and put a smear of 'engineers blue' marking dye onto the corresponding locking surfaces of the inspectors bolt. Insert this bolt RIGHT FORWARD, rotate it closed, then draw it backwards and forwards a couple of times to mark the mating locking surfaces of the rifle. Push it forwards, unlock and remove.
Examine the locking surfaces of the rifle. The blue witness marks should be evident. This ensures that whatever wear that has taken place on the rifle locking surfaces has taken place equally. If its not, then I'm afraid that the rifle is unserviceable.
BUT, that's not quite the end of the story because you won't have this 'Gauge, Inspectors, bolt' but it's only right that I tell you. Now for a little secret. If you have ever bought a rifle that has a sploge of red paint on the left side, adjacent to the internal left side locking lug, then you now know that the rifle was condemned for 'worn locking lugs'.
If you are going to fit a second hand or new bolt, then do the same thing. If the dye pattern is one sided, then stone the high surface of the bolt until BOTH locking lugs bear evenly against the locking surfaces of the corresponding surfaces in the body. BUT DO NOT ATTEMPT to stone the rifle to get a bolt to fit (you can only get to the right hand surface in any case...). The rifle body is induction hardened at these points to a depth of .004 - .006" but we have found it deeper.
Now that you have got the bolt fitting, with the locking surface bearings matched, it's time to fit a bolt head. Any one will do. Screw it into the bare bolt and test the CHS against the .064" GO and .074" NO GO gauges. ! Once you have got a fitted bolt, with CHS, we'll come onto bolt head overturn.
The bolt head should not overturn the long/top locking shoulder by more than 16 degrees but if you have a No4T or L42, it should not overturn buy more than a 'few' degrees. Mine were always 'in line' through selective fitting but you won't have a big tray of bolt heads to select from! The reason for this is because over a 'few' degrees (it doesn't define 'a few' but use 2 or 3 as your MAX), the recoil is taken on the bolt head and bolt threads. That is OK, but on an accurate No4T and L42, we want the recoil to be taken on the face of the bolt and transmitted radially, down through the bolt head and onto the front flat surface that mates up to the bolt head. Got it?
Now we have a correctly fitted bolt AND bolt head AND CHS. That wasn't painful was it? During the week, we'll go into striker protrusion, bolthead lift and anything else. But before we do, I want you to get your strikers and roll them along a flat surface (overhang the collars of course) and sift out the bent ones because they're going to cause you trouble. It's always the 1/4" BSF threaded end that's bent and you can only TRULY straighten them if you have access to a lathe. [/i][/i]