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I am assembling a new bolt head of matching #0 as insurance against leaking Winchester 41 primers. The one obtained looks new of finish, and doesn't look like it will line up with the rib without some help.
I understand there was a tool for helping bolt heads fit. Have no such tool and suspect they are not common.
Asking if anyone has a preferred technique they can share for helping a new bolt head to rotate fully onto a bolt body.
Firstly you do realise that not all number '0' bolt heads are the same 'size', '0' is not a size it is just a number. I have seen a number zero bolt head of 0.616" and as big as 0.636" so 20 thou difference between them, the nominal 'cluster' of size zero (it is a bell-curve) is between 0.626 and 0.631, still 5 thou, which could make a big difference if your headspace is towards the top end of the spec.Quote:
Originally Posted by togor
How did you determine that you wantd a number 0 bolt head ?
Regarding getting it to 'clock' correctly the tool was used if it was just a few thou off being correct, some bolts / bolt heads would just not align as the start point of the threads can be 'anywhere'.
If you read Peter Laidlers notes on bolt head selection you will see that the Armourers would have trays with dozens of bolt heads and they would have to go thru them to find one that gave the correct headspace, and, the correct clocking. The chance of you buying one bolt head and it meeting all the criteria is fairly remote.
Fitting bolt heads requires all of these things to be in spec. Guessing it's what AdE means by clocking since all of these things come into play when fitting together bolt assemblies. If your original bolt head is in spec, why change it? I wouldn't agree that "leaking primers" is a valid reason. I don't think that WRA ammo has leaking primers. I shot quite a bit of it 40 years ago, reloaded some of the brass too and never had a problem with it in rifles.
1. Bolt head overturn
2. Striker protrusion
3.Cocking piece lift
4. Bolt lift
5. Headspace
Too, you can have an overlap of size where a "0" is smaller or larger than a "1" and a "1" smaller or larger than a "2" and so on. The numbers overlap. I think there's a size list on forum here somewhere...Quote:
Originally Posted by Alan de Enfield
Too, I think a leaking primer could be construed as a pierced primer. Which is a firing pin length issue...
Most of the bolt heads we're dealing with now have been previously fitted. The charts are nice as long as you have nos, never fitted boltheads. Once they've been fitted once, the sky becomes the limit and the only way you can start is by checking for overturn and measuring them.
Well I intend to check the dimension between the bolt face and locking lugs to make sure. I am not stupid about such things.
Hoping the threads on these heads are at least loosely timed and not completely untimed. Garand gas cylinder locks have untimed threads but this doesn't affect headspace.
I started into milsurps years ago on M1903s. Lord knows that rifle had a long list of problems, but by the 1940's it was a perfectly good bolt action rifle. They had worked things out.
This business of the bolt head...to me it just confirms the No. 4 rifle as yet another example of needlessly peculiar British engineering. Letting the quirks become the defining attributes when they should be eliminated.
Primers sometimes leak at the edge and leave an arc of etching in the bolt face. Some brass (commercial Winchester) is known for this.
Examine enough Russian milsurps and you will see plenty of these circular scars in the bolt face.
The dimensions you need to check are the actual length of the bolt head from the rear shoulder to the face, not the threads or distance to the locking lugs. Try and get a bolt head that has zero overturn. If they overturn more than 1/8", they are out of spec. Remember that .064 Go and .074 No-Go are the only measurements that matter.
I think you'll find the ring of erosion on just about any rifle bolt or bolt head that's seen lots of corrosive primed ammo.
I agree that is a perfectly sensible measurement.
However,
A small amount of overturn is considered "part of it", and so the bolt locking lugs are the best reference in my situation. FWIW I measure 4.200" between lug rear and bolt face on two original bolts with original bolt heads, with the head aligned to the rib.
Looks to be roughly 5 degrees of rotation for a 0.001" change.
My new head is still under rotated, but also slightly long. Metal removal appears an option.
When I mentioned to a mechanical engineer buddy this bolt head business, how the recoil is taken on the threads (unless the head bottoms out perfectly, which I think would be rare), he found this to be a bad idea.
I produced this list many years ago - it has been updated with more results but cannot find it at the moment.Quote:
Originally Posted by browningautorifle
Didn't work - formatting gone all to cock !
If a bolt is clocked in spec, the threads do not bear cartridge thrust in practise. Bolts are made of hardened steel, while bolt heads are made of either wrought iron or mild steel that is hardened on the bolt face and the rail lip. The threads aren’t hardened.
So if it’s clocked in spec, the bolt head will bear on the bolt face after the first few rounds are fired, as the threads will plastically deform enough to fit itself more fully to its bolt.
Yes, I've had that and sometimes a bit worse.Quote:
Originally Posted by togor
^^^^^
The backthrust is not taken by the threads, but by the rear of the bolthead being in contact with the face of the bolt body.
If he's "blanking" the primer, with bits of primer cup actually blowing into the bolt, that would be a clearance issue between firing pin and the hole in the bolt head, necessitating bolt head replacement. I recently replaced an AR-15 bolt for this issue, after a few years of hot long-range loads went through it.Quote:
Originally Posted by browningautorifle
But if it's just etching on the boltface, I don't see that it's either.
Yes.Quote:
Originally Posted by MAC702
Agreed, I did one of those a few years back, had several fine pits burned into it.Quote:
Originally Posted by MAC702
To see if the firing pin protrusion is an issue it would need to be checked. One of the things you look at, when the parts get swapped by collectors there's little thought given.
Anyway, that wasn't the issue he was suggesting after all.
Quote:
Originally Posted by Claven2
Like this :
In both rifles I am working with, with original bolt heads, the back of the bolt head comes into contact with the face of the bolt body slightly past alignment with the rib. IIRC a few degrees of this is considered okay. I'm seeing about 1/8" of over-rotation possible at the surface of the rib.Quote:
Originally Posted by tiriaq
This means that when the bolt head is aligned to the rib, those surfaces are not in contact, and the recoil is on the threads.
Now as dumb beginners luck :) would have it, this new bolt head just purchased bottoms out exactly in alignment, *and* the measurement from bolt lug to bolt face matches the original bolt head to within .001" on the Maltby '42.
I agree that a proper set of headspace gauges is the way to really know what one has. But sometimes, if one is careful, a small incremental change from a known good system is possible without putting the rifle into a dubious state.
How would a new bolt head improve over what you have now?Quote:
Originally Posted by togor
As for the question of the threads "taking a beating" I'd suggest that the distribution of load over a dozen or more threads is far greater and the loading therefore much less than over the shoulders at the mating faces of the bolthead and bolt body. ;)
Well the design is what it is. :)Quote:
Originally Posted by Surpmil
I'm looking at a new bolt head not because of the thread pounding.
I'm looking at it because I might find myself shooting some 80+ year old ammo and I'd rather not etch the original bolt face if a primer leaks. Just a precaution.
Rifles have collectible value, so enjoy them, but take precautions.
I suppose they allow a little over-rotation in the fitting of the bolt head on the assumption that the bolt head and bolt face will take the pounding once the threads loosen up a bit and get out of the way :)
I wouldn't worry about it unless the bolthead you have looks sub-standard or compromised in some way. And if it does there are plenty of NOS ones out there you could replace it with if you have HS gauges or a vernier you can measure the existing one with. Only the HS gauges will show whether the BH face is square to the chamber of course.Quote:
Originally Posted by togor
As for the old ammo, be patient with hangfires and if necessary take advantage of the unusual ability of the rifle to recock without unlocking the bolt. ;)
Lee Enfields have HELICAL lock-up. Thus, basic measuring gear will be of little use.
It is "plug and play", all the way. According to ALL of the original technical literature I have seen, for No 1 Mk 111 rifles, there was ONE "standard" bolt head, with a "qualified" thread and a set distance (with the usual tolerances) from face to the shoulder forward of the thread. No "Shake and Bake" assembly here.
Caveat: POST WW2, (early 1950's), Lithgow did a run of "longer" series bolt heads. These rare and exotic items have LETTER size designations. If you have bolt-heads with a letter "M" stamped on them, that is NOT a "size", but indicated that hey were made from "Mild Steel" and then case-hardened and finish-ground. Earlier "unmarked" No1 rifle bolt heads were made from "malleable cast iron". The idea was to NOT have high "hardness" but general toughness. (Resist wear and NOT shatter in the event of a catastrophic cartridge case rupture. The entire purpose was the wring the last bit of functionality from the old girls before the mass adoption of the L1A1 rifle. These nifty new-fangled gas-operated jobs ALSO had a "graduated" locking shoulder system of inserts to achieve "spec" headspace AND "retention" grab". Once the gun-plumbers "ran out of numbers", the body was condemned and destroyed or used for "non-firing" roles like cutaway instructions rifles or as "levers" and such on grueling obstacle courses. (Try hoisting a succession of diggers in battle order over a ten-foot high wall, with an M-16). The FAL / L1A1 was ultimately late-19th century engineering with marginally better metallurgy.
My understanding from the instructions to armourers manuals is that the No1 MkIII bolt heads were anything but 'plug and play' with every one needing to be individually fitted to each rifle to ensure correct headspace and overturn. This is further supported by a post by Peter Laidler on May 5th 2008 where he states :Quote:
Originally Posted by Bruce_in_Oz
Spare bolt heads issued from the factory were actually oversize and marked with a small ‘S’….., but nobody can tell me by how much! Other Armourers of the period have told me, only yesterday over a frantic phone call, that this is incorrect but they WERE all to the longest specification.
Whatever it is/was, there should be room to stone to size. And THIS is where Armourers were always taught DON’T OVER CHS. Or in this case, should that read don’t UNDER CHS. If your rifle closes on the .074” NO GO gauge, this is what you do. Go to the No1 bolt head drawer and select half a dozen bolt heads that don’t overturn by more than 10 degrees (later, 15 degrees was permitted to make best use of remaining spare parts stockpiles), the bolt face is not ringed sufficient to allow the escape of gas past the primer and the striker hole is not greater than .084” dia. Try them all until you get the best fit. If necessary machine or stone the bolt head square and true until it closes over the .064” gauge and doesn’t close over the .074” gauge. The point at which the bolt doesn’t close prior to the .050” limit is academic because so long as it doesn’t go/close, it’s passed the test.
Now, how you shorten the bolt head it is up to you. You can machine it in a lathe if you like but some are quite hard, or surface grind but I was taught that the best way was to rub the face down on a sheet of ‘400’ wet and dry carborundum paper on a sheet of glass, just covered in slow running water. Go round and round with equal pressure, rotating the bolt head slightly every so often, taking a gnats knacker off at a time for several minutes and trying it again and again. Every so often, smear a smidgin of engineers blue on the rear of the .074” gauge and close the bolt head lightly against it to ensure a crisp round witness mark on the face of the bolt. This is the acid test of it being perfectly square to the bore. Be sure to remember these old Armourers technical words such as ‘gnats knacker’ meaning something too insignificant to be measured and ‘smidgin’, indicating a quantity equivalent to a gnats knacker.
Then, of course, there were the two different (non-interchangable) designs of bolt heads - the Mk1 and the Mk2
(photo from member 'Bear')
I have to say some the writing here is the best on any forum I have seen in quite some time.
"Plug and Play" was probably a poor choice of terminology, especially with regard to the No1 rifle and its predecessors. The fitters had trays of bolt-heads that had passed metrology at a previous stage. At Factory level,they also has stands of bolt bodies..
The trick was to meet a number of "requirements", more or less, simultaneously. .
The overall length of the bolt head had to work with a striker to produce striker protrusion within tolerances. Pretty basic.
Then that bolt head had to thred onto the bolt body with "zero" underturn; (or it could not be fitted into the rifle "body") and a VERY small allowance of "overturn, so that the firing load was transferred to the interface of the bolt body and bolt head "shoulders".
The bolt body / bolt head assembly then had to produce correct headspace (within tolerances) in the designated rifle body/ barrel assembly.
Meanwhile, the striker had to fit FIRMLY into the cocking piece. it is, effectively an interference fit; the firmness of the alignment is NOT determined by the thread, but by the short parallel sections forward of the thread in BOTH components. If this fit is NOT seriously firm, the cocking piece will "float" and engagement with the sear and safety mech will range from "annoying" to "BLOODY DANGEROUS".
The safety catch and locking bolt had to work to inspection standard with the cocking piece and the trigger and sear. Additionally, the cocking piece also had a very tightly specified set of angles and travels.
How many variables can dance on the point of a firing pin (striker)??.
Just for giggles, the barreled a bodies had a "different" chamber; slightly undersized.
The entire mechanism (sans wood) was fired with a "special" proof round. This was intended to "shock" fit the barrel to the body and "final seat" the bolt locking lugs into the shoulders in the body.
The 19th Century was an "interesting" place.The myriad changes to virtually EVERY component, (apart from the stock bolt in the butt) to produce the no4 basically HAD to happen, otherwise the rapid, mass transfer of production to "subcontractors could not have happened as smoothly.
The No1 rifle was essentially the product of a very "upmarket" Khyber Pass system, the No 4 borrowed somewhat from the automotive industry. No1 rifles are full of weird "Enfield Special" screw threads. No4 rifles went with "British industry standards like BA and BSF, thus the components could be 'farmed out" to a myriad small engineering shops. The tooling used to form the threads used pre-existing cutting tools and more importantly, "industry standard" precision gauges to CHECK tool wear and the threads cut with these tools, at factory level.
Quote:
Originally Posted by Bruce_in_Oz
All of the above is true, it was simply the choice of the words 'plug and play' I was questoning, as a newbie to LEs would take that as meaning 'take a bolt head out of the tray and it'll be the correct fitting, working perfectly', which we all know, is not very likely.
Somewhere in that tray of a 100 bolt heads is (maybe) the 'plug and play' bolt head, but finding it is not easy.
The bolt head chart that was on here a few years ago think ADe was updating it (Think he was the OP of it).
Yes it was mine.Quote:
Originally Posted by CINDERS
As you can see you can have a number '0' that is larger than a number '3' so specifying I want a 'number 3' is pointless, it is important to specify the actual measurement you need.
This was part of the original post I made :
Very few of us will have a bucket-full of bolt heads to work with so we need to have an idea of what bolt head size we need to overcome the headspace problem, headspace gauges will tell us it fails but not by how much.
A simple way, that gives a close approximation is by using a case and a primer :
Since the 303 headspaces on the rim, its headspace is the distance from the front of the rim of a seated case to the face of the bolt. To determine that distance we:
• Measure the rim thickness of a new case. A fired case will have expanded and closed the headspace. You must use a new, i.e., unfired case. Measure around the rim and use the highest value obtained. For an example, we'll say it measures .062".
• Take a fired primer and start it into the unfired case's primer pocket. Seat it just enough that it doesn't fall out.
• Hand chamber the new case, and slam home the bolt, seating the fired primer with the bolt.
• Remove the case from the rifle's chamber, and measure the distance the primer protrudes from the case head. For an example, we'll say it protrudes .014".
• Add the rim thickness measurement to the primer protrusion measurement and you have your rifle's headspace, at least you have a close approximation of its headspace.
In our example, 0.062" + 0.014" = 0.076"
Thus if your headspace comes out at 0.076” and your bolt head is currently 0.630” then you’ll need a bolt head a minimum of 0.002” (two thou) longer but ideally somewhere between 0.002” (to give the 0.074” max) and 0.012” (to give the 0.064” min).
Instead of specifying “I want a number 3 bolt head” you can now look for a bolt head between 0.632” and 0.642”
That was the one I was referring to. I've used it myself in past. The information is very clear.Quote:
Originally Posted by CINDERS
Just to clarify slightly Togor, if that's needed: the reason bolt heads can be found with such widely varying or inconsistent measurements relative to their marked lengths is mostly due to previous grinding and lapping by owners or armourers, rather than poor QC in manufacture.Quote:
Originally Posted by Alan de Enfield
Generally speaking you can be pretty confident that the 0,1,2,3 size marking does indeed reflect a longer bolthead, but by exactly how much? The original size difference was 0.003" between each number.
Civilian owners including myself, tend to want the bolt to just close over the "0.064" GO gauge, but anything between 0.064" and 0.074" was considered acceptable so there was little need to grind boltheads unless as the manual says, the bolt would not close over the 0.064" GO gauge.
There's really no substitute for the correct gauges.
Yeah it all makes sense now.
In my case, both the original and "shooting" bolt head gauge between .628" and .629". And the replacement bolt head times up right on the rib. Just waiting for an extractor screw and better weather.
Quote:
Originally Posted by Surpmil
That would certainly account for 'undersize' bolt heads but not 'oversize' (outside of the expected) bolt heads.
What Size Should The Bolt Heads Be ?
It seems to be generally accepted that No4 / No5 bolt heads should fall in the following range :
Size 0 = 0.620” – 0.625”
Size 1 = 0.625” – 0.630”
Size 2 = 0.630” – 0.635”
Size 3 = 0.635” – 0.640”
Whilst I don’t question that this information is printed somewhere, I have not been able to find the original source, the information I have found does not actually state the ‘starting’ dimension, only that the sizes are incrementally larger :
a) From “Parts Identification List Rifle No4 Mk1 and Mk1*” dated 1945
Bolt head 0 part number BB8584
Bolt head 1 part number BB8585
Bolt head 2 part number BB8586
Bolt head 3 part number BB8587
“Number 0 to 3 increase in length by increments of 0.003 inch”
b) From Canadian National Defence Manual “First Line Maintenance Instructions Rifle No4, all marks” dated 28th June 2002
Bolt head size 0 NSN = 1005-21-103-1143
Bolt head size 1 NSN = 1005-21-103-1144
Bolt head size 2 NSN = 1005-21-103-1145
Bolt head size 3 NSN = 1005-21-103-1146
“…….. the sizes being progressively larger in increments of 0.08mm (0.003”)
What I cannot find in any document is the 'starting size' of the #0 bolt head such that the 0.003" incremental increase per number can be referenced.
Just be aware that to tight is just as bad or worse than too loose. The .064 to .074 allows for rim thickness which does vary quite a lot.
If reloading for more than one rifle keep the brass for each rifle separate from the others use a LEE Neck sizing die only until a Full length sizing is required then only the minimum amount needed to chamber testing for case head separation before each reloading. That is before primer ,powder, projectile.
That is a very valid point - setting your headspace 'tight' to work with a SAAMI case with a 58 thou rim, then try and use a 'proper' military spec round with a 63 thou rim and you'll not be able to close the boltQuote:
Originally Posted by Bindi2
I think segregating brass is worthwhile if you shoot multiple 303 rifles regularly and if you don’t have large supplies of brass.
I have one set of brass for a rifle I shoot regularly and size gently, and another set that gets full length sized and used in whatever rifle. Those cases give fewer reloads, but it’s convenient and I have lots of brass.
I used to separate my brass then just neck size, but when you have a number of 303's your fueling it gets tedious.
What I found is my reloads whilst close to the MKVII specs they are not hot by any means and still fairly accurate good enough to win a 3 range multi-position match anyway.
I FLS all of them now but have found annealing them before sizing with my AMP machine seems to work in relation to brass longevity as it has been a fair while since I had a H/Sep probably get one this w/end but one always carries a B/C extractor.
Some rifles do seem to have a maybe slightly larger chamber as exhibited by a ring just above the web of the fired case I am fairly lucky as none of my shooters exhibit this fact.