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Was looking at an attractive 1926 Ishapore FTR with a '45-dated barrel (all serial numbers match.) Noticed that there was a bit of a gap - maybe 1mm? it was quite small - between the barrel and the receiver. Is this normal? unusual? safe? cause for concern? I don't recall seeing a gap like that on any of my other Enfields.
Not normal. Suspicious even. Without a full teardown, I'd pass. Unless you are just buying it for the receiver date, but then it's worth maybe US$30-40? Plus whatever the rest of the parts are worth- if you need them.
Oh, and welcome to the forums!
I suspect others will enjoy giving you the technicals on why the gap is "bad". So let's see who wants to contribute. (Theoretically, it MIGHT be OK to have the gap on a "range rifle" under certain circumstances, but it's not acceptable on a military build.)
Thanks for the welcome - I have lurked here a bit, done a good bit of reading, and see some familiar names - some folks will recognize me (and this question!) from other forums.
I'm wary of the rifle and likely will not buy it - my small SMLE armory is mostly Australian - but I'm hoping to at least learn something of a technical nature, perhaps about the rebarreling process and such.
Just for the record:
SMLEs breech up on the INNER breech ring; that is, the inner ring where the bolt head seats.
No.4s, however, breech on the front face of the receiver. Then there are the 7.62 NATO converted No4s that use breeching washers between the receiver and Knox form.
NOTE ALSO that Mauser 98s are also SUPPOSED to breech on their internal ring AND have 55deg Whitworth- form threads. Few, if any, commercial barrel-makers around the place seem to follow either of these practices.
A SMALL gap between the receiver and Knox form on a SMLE should be OK; on a No4, probably not. I understand that it has something to do with both the theories/observations of thread-crush and the manner of gauging used to select components.
But you wouldn't consider a 0.025"/1mm gap small would you?Quote:
Originally Posted by Bruce_in_Oz
Usually, when I see this sort of gap, there's also a small deformed area on the back edge of the reinforce that screams "previously installed barrel"!
Theodore: Do you have a set of feeler gauges you could use to get a precise measurement? 1.0mm is quite a large gap (0.039inch). I'm also curious as I have a SMLE with about a 0.010inch gap.
Ridolpho
I don't, but they may have one at the gun shop where the rifle is for sale. I'll go by there and ask.
Theodore, the first thing you must do on Monday morning is to go and invest in a good set of feeler gauges. This is the most important part of an Armourers tool kit. Not only an Armourers, but for anyone who is remotely interested in shooting.
That's the lecture over with............. To the rifle. I can confirm exactly what Bruce in Oz says and it's correct. There can be a small gap between the nocks form part of the barrel breechy and the front face of the body but it will only be marginal, say .020" or so and this is because of the +/- tolerances between the breeching up threads and distance to both stop faces.
I can't see any mention of an allowable gap during breeching up but purely from the practical point of view, if the barrel is breeched up on the inner surface of the body, then even a .100" gap would be academic. It'd be unsightly of course but still academic! Anyone agree or disagree with that? My little No2 has a little .012" gap that's just full of oily crud
I agree with it.
I poked around looking for a barreled action with a gap (Mostly Indian rifles) to photograph, but couldn't find one in the pile. Anybody have a visual aid?
Thanks for the correction! Stupid of me, but considering that I'd been up for 23 hours at that point, stupid is normal...Quote:
Originally Posted by Ridolpho
was heading down to check when I finish reading...Quote:
Originally Posted by jmoore
Here's the gap on my 1923 EFD Mkv SMLE
https://www.milsurps.com/images/impo...rrelgap1-1.jpg
https://www.milsurps.com/images/impo...rrelgap2-1.jpg
https://www.milsurps.com/images/impo...rrelgap3-1.jpg
Overall it looks fairly small, but is it consistant? In the first shot it looks 0.010" or less.Quote:
Originally Posted by 5thBatt
Good visual aid!
And on a rifle built during a "quiet time" when the production pressures were low.
Well Theodore, if you have'nt got your answer yet, there is none.
The forum with the resident armchair collector has locked this thread, let's all just leave it at that.:nono:
Amen to that.Quote:
Originally Posted by muffett.2008
He was making my eyes bleed!
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did Lithgow make armchairs?Quote:
Originally Posted by muffett.2008
I don't have one with a noticeable gap, but take my hat off to 5thBatt. Thats a great example of what the sav said cannot happen!
jmoore, the gap is consistant & appears to go all the way to the thread, here's a photo to compare.Quote:
Originally Posted by jmoore
https://www.milsurps.com/images/impo...lthreads-1.jpg
SMLE breeching data:
According to drawing No. A.I.D. 1318. to accompany S.A. 435A, the pertinent dimensions are thus:
From receiver front face to forward face of inner breech ring: 0.681" Accept, 0.689" Reject.
From absolute end of barrel to shoulder of Knox form: 0.6911".
Thus, under any acceptable gauging, there should be a SMALL gap between the front of the receiver / body (or "shoe" if you prefer REALLY old Snider-vintage parlance) and the rear of the Knox Form. Therefore, SMLEs are INTERNALLY breeched, like a Mauser 98.
When I get a few hours spare, I will dive into the crypt and dig out the relevant numbers for the No4.
Here are a couple more
First, one full turn out.
Second, a gap of about 1mm.
https://www.milsurps.com/images/impo...poneturn-1.jpg
https://www.milsurps.com/images/impo...gaponemm-1.jpg
5Batt, the barrel you show looks like the relief undercut is not deep enough, not that it matters if the barrel locks up on the inner face, but it sure would be a problem otherwise.
Bugger.....I told myself to let this one go, but then again, now I am talking about machining practices and not that other crap.
DONT LET GOQuote:
Originally Posted by muffett.2008
The correct information must be out for all to see.
There is so few of you knowledgeable real life armourers of this vintage out there who can sort the B#$$ S&*T from the waffle.
A laymans book might be the go (hint hint) for PL or company
I thought we already had THE expert on the other forum.
Is that my hat and coat?
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Well I went back and looked at it again (without a gauge - sorry!) The gap is certainly far less than 1mm - in fact it looks to be even smaller than that on the 1923 MkV that 5thBatt so helpfully posted. So, nothing to worry over, I think, except whether to buy it.
Inter war year Ishapores are not common, i would buy it, but only on the condition the barrel doesn't fall off before you can get 10 shots away :)
Quote:
Originally Posted by muffett.2008
Quote:
Originally Posted by Homer
Y'all just about had me confuzzlated there. There's another Enfield site?Quote:
Originally Posted by gsimmons
BTW: Thanks, 5thBatt for your "above and beyond" efforts on this thread!
But, wait; there's MORE! as they say in the classics.....
After successfully tinkering with the lawnmower, I did a bit of a dig in the crypt.
No4 data re. breeching is as follows:
Distance from front face of receiver to inner breech ring: 0.701" + 0.005". (Taken from the 1961 version of the drawing for the Mk 4 pattern receiver.)
Distance from rear of threaded tenon to Knox form shoulder: 0.696" Max, 0.693" Min
Caveat; those figures for the barrel are from the drawing for the AUSTRALIAN "Barrel No4 .303 (AUST)" which was produced for the rifle clubs in the 1960s. The drawing is dated 12Mar1965 and the only obvious difference is at the pointy end. The muzzle has the external "cone" feature for easing the bayonet into alignment but is devoid of bayonet lugs. Do any forummers own one of these barrels?
There was allegedly a 7.62 NATO version of this barrel also produced at Lithgow, but I have neither a sample nor a drawing. Any clues?
Quote:
Originally Posted by Bruce_in_Oz
I've had a standard profile 7.62 No4 barrel, made at Lithgow, it was the same as the No4 .303 barrels, as you say with the cone, but no lugs. Both the .303 and 7.62 were superb shooters when set up.
The 7.62 barrel interestingly came with breeching up washers of about 0.070" as I remember, so the tennon was long by this margin. I sold the rifle since, and havn't seen another barrel like this.
Surely.................. It's a case of what I call in mechanical engineering terms, the bleedin' obvious! If there's NO gap between the front face of the body and rear face of the nocks form, how will you know whether the rear face of the barrel is breeched up against the corresponding face of the body? I say, let's cut out the crap and stick with the facts!
Quote:
Originally Posted by Bruce_in_Oz
Just one question here: What's the tolerance on the barrel end to knox form? Or is that a maximum drop?
According to the data above the gap can range from 0.002" (which, after all this time will likely be full of dried oil, rust, etc. and be unmeasurable.) to a "tenth" over 0.010". (Which would be about 5thBatt's first example.)
Good to have numbers, but after having a few barreled SMLE actions locked together to the point of having to cut one or the other to eliminate the seized juncture at the knox form, it's more than theoretically possible to have the two surfaces in contact.
Conversely, a 1mm gap would be well out of spec. (Even at 0.025" it's way big.)
Bruce, I still have a couple of the Lithgow No.4 barrels.......and they have the bayonet lugs.:confused:
Muffet:
That's interesting about your Lithgow No4 barrels.
So, there must have been two versions of the .303 No4 barrel produced at Lithgow. The drawing I have is Issue 8, and has notes referring to alterations to the bullet leede to be incorporated in all production AFTER 15 March 1965. Not having the earlier editions, I can't compare the leede dimensions, but I suspect that they shortened the throat from the old SMLE chamber spec. Remember that SMLEs, (at least at Lithgow),were throated to work with both Mk6 and Mk7 bullets. A shorter throat and different ramp angle would probably work better with the Mk7 bullet.
Just to be sure, I'll compare the chamber dimensions on my late-edition No4 barrel drawing with those on the 1920 and 1938 SMLE barrel drawings; could be interesting. While I'm at it, comparison of a "standard" SMLE chamber and one in an "H" barrel could be interesting.
This is real "Anorak stuff" as our English cousins would say.
Does anyone have the drawings from Savage or Long Branch?
To the Bat-Cave, Robin!!
Not only is it anorack stuff as the poms would say but what about the Army expression of '........mission creep' too?
The rifle is resting comfortably in my armory, 40 rounds later. The gap has not grown any and the spent brass is just fine. Obviously the armorers knew what they were doing when they built and rebuilt this rifle all these decades ago. I appreciate all the help, even if my wife does not. :rolleyes:
I'm glad despite all the bullsh....er....manure you got the rifle. I look forward to seeing the pictures.
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Since Theodore has a fine new rifle without dramas, it seems like a good time to explore this matter further in a general way.
I was able to round up a few loose actions, most of which haven't been touched since the barrels were removed. Almost all of these show signs of a gap at the front of the action body. One had good contact between the knox form face and the action front.
But what may be shocking to some of you is that several actions had no contact on either face! In fact some have quite the build up of crud on both faces indicating neither shoulder was responsible for retaining the barrel. Muffet.2008 has already commented in passing on the reason how this situation could occur. In fact, it makes perfect sense to me, providing a certain circumstance exists during barrel manufacture. Especially in a high production environment. (It also explains why many SMLE barrels are comparatively easy to unbreech, especially compared to No.4s.)
https://www.milsurps.com/images/impo...fe5e7d5d-1.jpg
Some surviving actions. Quite a few were scrapped. These had bad barrels.
https://www.milsurps.com/images/impo...b9402c1b-1.jpg
Here's a Bubba Special, now rendered down for it's last possibly useful assembly- IF a scoped action is needed. Note the lack of contact on both the front and rear faces after some clean up. Its matching barrel was easily removed.
https://www.milsurps.com/images/impo...806068e7-1.jpg
Definitely no contact on the rear face! Thick gunk build up remains.
https://www.milsurps.com/images/impo...04dbff14-1.jpg
This action on the lower right is quite nice. But the barrel was shot out to a point that it's rifling was very rounded. The throat was washed out and the muzzle? I think it wasn't bad. Hopefully it's still about.
At any rate, it had contact on both the front and rear face. Barrel removal wasn't easy on this example. It's supposed to be a DeLisle project...
I had to cut a few actions that had this double contact when they just would not unscrew. The barrels were good, but the actions had problems.- Including one which had a small opening on the left side, exposing the LH locking lug. A couple were twisted so badly a bolt would not traverse.
https://www.milsurps.com/images/impo...0c0f97eb-1.jpg
A few more. I'm beginning to see why the subject doesn't come up more often. Even a 0.010" gap would be almost impossible to detect after all the dried dirt and oil filled the recess fairly permanently! It survived unbreeching and years of rattling around in boxes, etc.
I've been wondering (since this topic came up) what issues, if any, there would be if a barrel was fitted without contact either end but was firmly in place & headspace was good??
I would think that because it wasn't "locked" between the front inner face of the receiver and the rear surfaces of the thread in the receiver, it would eventually loosen from the force of firing and turn. The thing to consider here is that a thread is an incline plain, (in two dimensions) and as such requires counter resistance to lock the two components together.
A standard form (V) screw thread might not be ideal as a load bearing surface, but this application also requires self locking ability. If a square form thread was used for example , it would bear the load much better, but no matter how tight it was, it would unscrew much easier, being an incline plain in one dimension only.
Having a barrel and receiver depending on the thread in both directions would mean that the very slightest impact wear would loosen them.
My thoughts, off the top of my head... who wants to shoot me down? :lol: :surrender:
I've been pondering the same too 5th Batt, especially after pondering the actions in JM's MOST interesting photos and observations. To be honest, if the threads don't lock by virtue of a stop surface (or other locking mechanism), then they'll be free to rotate, held only by friction. This would never be acceptable on a barrel due to the rotational forces applied by the bullet in the rifled bore - whether it's trying to loosen or tighten the barrel as it starts its journey. Just think of the barrel as a 1/2" UNF bolt in a nut for example...........
I'd have to say that if the barrel wasn't breeched up against a stop face, then you might well get CHS and it might well be tight but it wouldn't ever be tourque reading tight and therefore, technically, it'd be loose and as sure as god made little green apples, with the constant expansion and contraction (by heat and load) it'd work loose. That's just my thoughts, thinking on my feet as they say. Good question!
And here's another thing......... If the No1 barrel is breeched up at the end of the barrel face hard against the inside face of the breeching-up ring of the body, then what earthly use is the gas escape hole in the left side of the body? If it is to allow any residue of gas to escape (from a pierced primer for example or.....) then it must be a frill, if not a complete fraud if the barrel is breeched up hard against the body because there would be no passage available for any gas to escape - let alone bleed through the gas vent.
Can you get a close up photo of that configuration JM? Thanks
Peter, to save waking JM up, maybe a pic from my high tech photographic studio could provide the answer.... I wasn't sure of the inside view of this either, but now know the vent holes actually go through behind the thread, in the thicker part of the receiver ring around the bolt face.
Attachment 37085
Yep, got that now Son. Well done the Armourers! I only had a SKN action here to browse at, that's why I asked JM (sorry to wake you up JM.....) for an inside view. Problem solved. Thanks again. Arte et Marte
JM, did you check the undercut on the barrel's? to my way of thinking, if the undercut is inadaquate, the barrel will lock up where the thread ends, sufficient torque can be applied to get the barrel to clock correctly.
As the twist is LH, this would ensure the barrel is not likely to unscrew on firing.
I have noticed this problem a few times over the years, but never associated it with the factories, I always assumed some *** had done it post assembly, they say you should never assume.
Pardon the ramblings of a non-engineer (geologist) but the "inclined plane" of the threads is at a very low angle relative to the axis of the bore and the force directed along the bore by the shell head pushing on the body through the bolt will generate a huge amount of friction along the inclined plane- perhaps enough to overcome the torque generated by the bullet hitting the rifling?? All those actions displayed by Jmoore would tend to suggest losening by shooting doesn't happen. In any case fascinating stuff and highly educational.
Ridolpho
I have actually seen this slight rotating of a barrel before my very eyes.
I was stood behind a few soldiers zeroing in their SA80 rifles, just glancing occasionally while oooking through my binos..... only to see one group of shots gradually walking off the target so I walked over to the shooter and kicked his feet - as you do - and asked him why he was continuing to shoot off the target (I was a tad more forthright than that if you please.....). He told me that he was aiming at the bull and so far as he was concerned, that's where they were!
As I looked down at his rifle as he was shooting and could actually see the foresight cranked over to the left (or was it the right.....?). He couldn't see that the barrel or gas block seemed to be loose to point of unscrewing. I stopped him shooting and lo and behold, the barrel was just over hand tight but unscrewed using a spanner with no vice clamps.
Anyway, a barrel will unscrew if it's not tight!
There was a sequel............ He asked me how I could tell that the barrel was loose
Me: I could see the sight block over to one side
He: Well, I was still using the foresight and it was shooting OK
Me: I could see the shots getting further away from the target
He: How come..........? I was aiming at the bull
I thought about a technical answer but instead, just told him to get another rifle from someone else!
You got it! As you were about to drift onto the subject after viewing 5thBatt's photos, but managed to restrain yourself. But barrl photos will not be forthcoming today. Mostly because i haven't found them.Quote:
Originally Posted by muffett.2008
More details coming.
Bruce is that right that a mauser 98 is also breeched up internally? The same individual that persistently suggest that any gap present between action and barrel shoulder is a case of laziness and poor workmanship also suggest that the mauser is breeched up on the external face of the action.
Quote:
Originally Posted by Bruce_in_Oz
The Gew98 and following should have the rear face as the primary datum. The barrel reinforce at the front face should not be the primary locating feature, so, no, that other unnamed fellow is incorrect from a design standpoint. I'm not really a Mauser guy, but it shows up in print often enough and with references to German documentation...Quote:
Originally Posted by Homer
For a good breakdown of many turnbolt action designs in great detail try The Bolt Action: A Design Analysis, Vol. 1 by Stuart Otteson. No Lees, unfortunately!
Which, to continue with the tangential nature of the subject, leads to Lee's last design, the 1899. In which, much to the consternation of most anybody interested in design and manufacture, has locking lugs both toward the rear and front of the bolt! Imagine trying to get all four lugs to bear in a production environment. The horror...
https://www.milsurps.com/images/impo...DSC00056-1.jpg
Not to mention that the bolt head is a separate piece, AND that the lugs are at 90 degrees to each other.
https://www.milsurps.com/images/impo...DSC00060-1.jpg
The horror...
:runaway:
:p
This makes perfect sense and why would they complicate the procedure if it wasn't completely unnecessary.
=Peter Laidler;237253]Surely.................. It's a case of what I call in mechanical engineering terms, the bleedin' obvious! If there's NO gap between the front face of the body and rear face of the nocks form, how will you know whether the rear face of the barrel is breeched up against the corresponding face of the body? I say, let's cut out the crap and stick with the facts![/QUOTE]
Sorry I've been replying to post as I've been reading through the entire post and just got to jm's post. Fascinating really. I would have thought surely one face must be bedding down in order to torque up the barrel unless the thread is bottoming out.
Edit. And now I've just got to muffers post mentioning the thread. I'll try to keep up from now on.
Here is another in my collection with a gap, this time a 1893 MLM MkII with its original Metford barrel
https://www.milsurps.com/images/impo...3mlmgap3-1.jpg
https://www.milsurps.com/images/impo...3mlmgap2-1.jpg
https://www.milsurps.com/images/impo...3mlmgap1-1.jpg
That looks like the gap ought.
Your Mk.V is the suspicious one.
Been trying to find my feeler gauge to measure the gap on my MkV, if i dont find them over the weekend i will buy a new set.Quote:
Originally Posted by jmoore
Found some pull offs. (Found more after taking these photos.)
The significant feature is the lack of a thread relief at the front face junction. Quite mad actually! All of the load (90% or so) is taken by three-four threads. So, losing a thread or two here would mean nothing! Having to run threads to a hard stop means that the cutter was quite fragile. Even if some sort of die was used. So it would be quite easy to have an oversize condition in an area that's hard to measure. Which could easily cause the barrel to stop rotating early. The natural reaction would be to remove metal from the rear face. It's where contact is supposed to occur, after all. Trim off a bit and try again. And so on. If cutting the rear face didn't work, the next most likely step taken by a hurried factory fitter would be the front face. Redoing the thread? Out of the question for that particular machine operator.
But it seemed to work in these instances anyway. The ones that loosened prematurely were rebarreled long ago. The "thread lock only" works partly because not much force is required to secure a barrel for shooting purposes. Just ask the benchrest crowd. It was helped by the fact that the No.1 had the bayonet attachment separate from the barrel, so no external torque loads would be applied except during front sight adjustments.
https://www.milsurps.com/images/impo...f61fa257-1.jpg
https://www.milsurps.com/images/impo...ffb0dfa3-1.jpg
This barrel pictured above and below is one that made both front and rear face contact, BTW.
https://www.milsurps.com/images/impo...e5be2d29-1.jpg
https://www.milsurps.com/images/impo...a8119379-1.jpg
But even when rear face contact is made, too much can be bad. Here's a badly galled example:
https://www.milsurps.com/images/impo...6b1f6acb-1.jpg
Here's a scrap No.4 barrel that shows a much better threading design with a nice relief cut that makes both threading and setting the front face dimension easier . (Disregard the extra step cut into the shoulder during removal.):
https://www.milsurps.com/images/impo...7e8af081-1.jpg
Muffet.2008 might be able to 'splain all this better. (He already knew the drama.) Or any number of our fine mob...
I don't think I need to JM, your pic's show it all, but to add a simple explanation for the uninitiated, by cutting a thread relief (removing the last two threads near a shoulder) allows the component to be locked up against a face with no binding of the threads, or step cutting (cutting a relief in the female face) to achieve the same thing.
This relief or undercut assists the machinist when thread cutting also, it would appear by those pics that the barrels were actually threaded on a die rather than a lathe, I guess that would certainly speed up production, it may also explain the misaligned thread on the third barrel from the left, or is it just my eyes?
Thanks JM, that's a great result and certainly brings the answers to the original posters question:super:
Receivers and barrels, especially in Lee Enfields are relatively "soft" and thus ductile.
Therefore as the barrel is wound in past he point of initial "seating", the threads will start to take up the load. It doesn't much matter whether the barrel is internally (SMLE) or externally (No4) breeched. Because of material yielding the load will be distributed. In high-grade tthreaded material (Grade 8) for example, there is pattern of load distribution on consecutive turns of the thread, along the lines of 35%, 25%, 15%,10%,9%, 7% and so on.
Essentially, approximately 75% of the load is taken on just three turns of the thread. In more ductile material, like SMLE receivers and barrels, the load will be distribured over more threads because of material crush. If you want to achieve better load distribution in harder materials, you need to produce exceptionally accurate and finely finished threads. The ductility of a material actually HELPS surface engagement, It just may not like being flogged repeatedly at 55,000 PSI plus.
There is NO significant improvement in shear strength if the thread engagement length is greater than the screw major diameter. An engagement length of 1.5 times diameter MUST, in ALL cases, provide at least ONE good turn, which will take up all of the load. Further axial stress will cause thread crush and start more thread engagements. (Up to a point).
Basic rule is that an engagement length equivalent to 80% of the nominal diameter will mean that the screw (internal fastener / barrel thread) will fail in TENSION before the receiver (female thread) fails in thread-stripping; assuming similar material properties.
Lee Enfield tenon threads are a little shorter than their nominal diameter, however, the "thread-loading" percentage rule applies. Basically, you will blow the bolt out sideways (because of the nature of the stress paths between the barrel and the locking shoulders) before you shoot the barrel off the front!
OH NO :yikes: WE ARE ALL GOING TO DIE :ugh: :eek: :move eek:Quote:
Originally Posted by bruce_in_oz
hahaha... can't wait until somebody :madsmile: comes across that line in a google search! :lol::lol::lol::lol::lol::lol::lol::lol:
Savage shooter, alias LE owner, will have it up in the next post.:madsmile:
Just happened to see this thread, and maybe comment is pointless, but I have an ENVOY which is breeched up this way: tight against the front or outer face of the body and against the inner face of the body at the bottom of the barrel thread recess. I'm not sure how the smith set it up, but he's done quite a few. I suppose he could measure the distance from the front face to the inner face with a depth mic if cutting the threads/shoulder on the barrel. Or if it was an already threaded barrel, screw it until it sits tight against one face and use feeler gauges to determine the distance between the other face and the body face, then remove the necessary amount of metal from the 'prouder' of the two, until the distance between all four faces is identical. The barrel should then screw in with both faces meeting at the same time, and compressing to the same extent as the barrel is tightened.Quote:
Originally Posted by Peter Laidler
I assume!
Generally both faces engage on Mausers as well. With the primary datum being the rear face against the internal collar.