Thread: SMLE barrel torque?
Retrieved: 06/18/2014

Okay, I made some tools and got the barrel off the receiver.

Does anyone have the official torque spec for installing a barrel? I already searched this topic with the keyword "torque" and didn't find a number.

ronn38
Dec 20, 2010

I don't believe SMLE barrels are installed via a specific torque, like head bolts on en engine block. If indeed they are, they would be somewhat unique in the gunsmithing world. The barreled is tightened until correct headspace is achieved, which identified via the used of a 303 (I'm assuming the caliber of your rifle) go and no-go gauges.

But maybe a SMLE expert can correct me and help you out.

TRX
Dec 21, 2010

A factory replacement barrel might have the threads clocked to the proper position, but I have a threaded blank, so it has to be torqued before it can be headspaced, cut for the extractor, etc.

ronn38
Dec 21, 2010

Ah, I hear what your saying. Are you rebarreling it to 303, or are you doing a wildcat? I've always thought the Enfeild a very slick action to build a quick sporter on.

TRX
Dec 21, 2010

I had a naked No.4 receiver, and have collected a bolt and various bits to make a rifle, including a .45-70 barrel.

"No salvageable military rifles have been hurt in this project."

SavageShooter
Dec 21, 2010

I'm no authority on the subject but I think the average torque for a centerfire rifle barrel is 60 ft lb.

The Enfields, with exception of the P14 and M1917 rifles which were torqued down by machine, were pretty much torqued down by feel.

I've watched an experianced gunsmith as he torqued down the replacement barrel of my old Garand, a rifle that also requires precise clocking in to keep the front sight base level.

He'd tighten it down till it had the feel of correct torque, check the indexing, then back off and try again till it had both the proper indexing and correct feel.

The Enfield barrels have an undercut shoulder with an edge that is crush fitted to the receiver ring face. Once the shoulder crush fits, if it is still not properly clocked in it can be backed off and crushed down a tiny bit more till indexing and feel are correct.

If a No.4 or No.1 doesn't headspace within limits the only recourse I can see would be to grind the surface of the internal shoulder of the receiver ring. The breech butts up against this shoulder so it limits just how deeply you can screw the barrel in.

A diamond coated disc is used, by the gunsmith I mentioned, to blue print mauser type actions, for truing the locking surfaces.

The same sort of set up could be used to face off the shoulder of an Enfield receiver ring.

The smith used cut off barrel shanks bored out as a guide for the shaft of the diamond coated disc. He'd remove no more than a couple of thousanths due to the thin carburized layer of the Mauser heat treatment.

A possible alternative would be to turn a sort of ring or flange in the breech, the same diameter as the opening in the internal shoulder. That way the headspacing of the rimmed case on that ring, which would protude past the shoulder, could be altered as neccessary.

ronn38
Dec 21, 2010

45/70 sounds very fun! I've often toyed with the idea of building a /405 Winchester on a No.4 action.

TRX
Dec 21, 2010

The .405 would be a good choice, except the .411 bullet diameter is a real oddball. That means there are no inexpensive barrels to be had for a .405 conversion. Given how nice the cartridge is otherwise, that's probably the main reason you see so few non-factory .405s.

Last time I looked at SMLE conversions I found a lot of people talking about .444 Marlin, I failed to find anyone who had actually done one. Unlike the .405, .429" barrels for the .444 can be had reasonably. I don't know if there's some hidden gotcha, or if it's just that nobody likes the .444.

Alan De Enfield
Dec 22, 2010

When breeching up a whole raft of things come into play:
a) Extractor slot aligned with extractor
b) Sights vertical
c) Headspace
d) Torque
e) Overturn / underturn

If you are talking a No.4 then the following notes from Peter Laidler (on the old Jouster Forum) may be of assistance:

Hello from wet, miserable, rainy Warminster, home of the Infantry, where Salisbury Plain has turned to mud. Ah, yes, breeching up.

I wonder how many of you read the thread on our sister Enfield collectors milsurp site regarding take-off barrels and the problems re-indexing them when used in another rifle afterwards. This is nothing new, not even with NEW barrels, especially 'new' old 40's barrels that were still in the system until a few years ago. And dare I say it, but Savage spare barrels seemed to be the worst offenders.

At our big field and base workshops it wasn't such a problem because we'd usually have a long racks of barrels, both new and almost new that we could use until we'd get one with the correct "hand-tight" underturn that we could select for final fitting. Oh, yes... before I forget, we always graded our barrels in quarters of life. If a barrel was in its first quarter of life then it'd be almost as new and so on to a last quarter of life where it was probably shot out. But shot out didn't mean that it was duff or inaccurate either. Anyway, I digress... But don't get the impression that it was just barrels where the breeching up threads were slightly out of index. It was the rifle bodies too. And if you got a rifle where the breeching up thread was "late" (that is, commenced even a minute of angle late), then getting a barrel that would underturn was difficult. So I'll take you through what could and would happen.

Sniper rifles were the worst because they were always at a premium and the Command AIA, (the Assistant Inspector of Armaments) would always specify new barrels for these but that was easy to say but sometimes difficult in practice. So where a new barrel couldn't be found with the correct underturn, the breeching-up face of the body would be smoother-off with a smooth file, just a gnats knacker or as you wild antipodeans or colonial savages say, a RCH so that a datum surface was available. Then the best-fit barrel would be fitted until it read the correct underturn THEN a reading would be ascertained as to the thickness of material required to get the correct underturn. Lets say that in our case, it was .028". That's twenty eight thousandths of an inch.

Someone suggested that his gunsmith will insert a .028" steel shim and that's the answer. Others have suggested that it'd be a good idea to gently swage the shoulder of the breeching-up face of the barrel, sufficient to take up the slack. DO NOT USE THESE METHODS. THEY ARE XXXX POOR ENGINEERING PRACTICE and verging on the best bubba practice you will ever have the privilege of seeing. Have you digested that?

This is what you do. Knowing that your barrel needs .028" underturn, get yourself a proper breeching up washer made. I'm not going to teach you or your machinist pal how to suck eggs but if you need .028", then get the breeching washer made .128" THEN machine .100" off the breeching up face of the barrel (no, the breeching UP face, not the BREECH face silly...). But I'll let you into a secret. At our large Base workshop in Singapore, we were running major overhaul programmes of everything including L1A1 rifles. Then, someone noticed that the tough, hard, readily available and exact diameter required L1A1 breeching up washers were between about .055" and .070" thick. Now, we'd just take the barrel to the little Chinese fitter/turner (he had a big pile of breeching up washers in his tray anyway) and say '.028" please Lim' and he'd mount the barrel and machine away .032" from the breeching up face. You'd walk back to the Armourers shop, past Steve's Magnolia ice-cream van where you'd spend the next half an hour discussing politics or the Viet- nam situation or the new flower arrangement in the church with the rest of the blokes... Oh, I've gone off at a tangent again... Anyway, armed with the new barrel with .032" machined off the breeching up face PLUS a new .060" L1A1 breeching up washer you'd know that .060" - .032" was .028" which is JUST the underturn we need to tighten the barrel to make it PERFECT on the flat-plate we used to ensure that it was perfectly tight, upright and square.

Is that simple enough? It might be a tad more thoughtful that a steel shim or a good battering around the barrel flange that won't last twenty minutes but it's how the pros do it.

There are a few afterthoughts too. I'm telling you this so that when YOU need to do the job, then YOU tell your gunsmith how its done properly. And go and buy a selection of L1A1 breeching up washers now, while they're available. When a badly shot-out/rusty bore No4T Lyman TP rifle was recovered recently, it too overturned by as much as it should have underturned, even with a new barrel. Our main workshops were at their wits end as there were only a few barrels from which to select. So what method do you think THEY utilized? Yep, got it in one. And it shoots as sweetly and accurately as it ever did. And as for us young 20 year old lads discussing politics, Vietnam or Flower arranging in 60s Singapore... then if they did, I wasn't part of the discussion!

ARE YOU ON THE SQUARE? A guide to breeching up!

ON THE SQUARE

As a result of a request from forumers, I'm going to tell you how WE, the REME Armourers breeched up No.4 and 5 rifles. And while we're at it, this is the principle of how we did L1A1s too.

I must stress that we were all taught the correct method of breeching up but to be honest, and I'm going to be simple now, you were relying on a parallel gauge, one end of which crossed the flat we call the KNOX FORM. And as you are well aware, while it is meant to be a datum surface and therefore accurate, in MOST cases so far as I was aware, it simply wasn't! What I'm going to tell you ignores the relationship of the Knox form with this that and the other and relies on good, sound, honest, common sense!

You have all (hopefully) read the previously published article about how we would select a barrel from a large rack of 'em, that gave us about 18 degrees or so of underturn. If it was, say, 25 degrees, then you simply skim a gnats knacker or a RCH from the breeching up face. If it's, say only 10 degrees, then you insert a breeching up washer to suit. Has all that stuff been read and digested?

Someone asked a couple of questions/comments about the breeching up washers after I said that we used the plentiful L1A1 washers. And simply put, the L1A1 washers are a good fit and do the job perfectly. As for the quality, well, simply put, they might not be HARD, as in mechanical engineering terms but they are TOUGH and that's what counts in this application.

When you have breeched up your barrel so that it LOOKS pretty-well square, I want you to select a solid (as in not the fabricated type) foresight protector with straight and undamaged sides and secure it to the foresight block band When the screw it tightened up, this foresight protector should grip the block band each side. In other words, even when the screw is loosened a tad, you should not be able to rotate the protector... not even a little bit. It must slide and sit on the foresight block band tightly.

Now you probably won't have a hundred or so foresight protectors to try before you get one that's perfect. You won't need that many, and most probably, the first or second you try will do. If you can't find one, then just make sure that before you tighten yours up, then it is sat EXACTLY equidistant/centrally astride the block band. Do you understand this. It is important.

As a matter of interest, we had an exact protector that was painted BFA yellow (that's Blank Firing Adaptor paint colour...) that stayed with the breeching up kit together with an extended screw with an allen-key end for ease of use but I digress...

Now, you insert a 4' long or so .144" diameter or 9 SWG (Standard Wire Gauge) ground steel bar, through the backsight axis pin hole and rest this across two matched vee blocks that are sat on a surface plate at a height that allows the rifle to lay parallel to the surface plate or something else that is 36" or so long and absolutely FLAT. We had a sheet of plate glass that did the job as well as anything. Now, allow the foresight protectors to touch the glass. Now, gently rock the barrel and the body between the axis pin and the protectors. It SHOULD sit absolutely square, supported between the axis of the backsight axis pin and the square of the foresight protectors.

If it's not EXACTLY square and rock free, then just tighten or undo the barrel a further gnats knacker until it is "no-rock" perfect. And that is it! If we were 2nd Class Craftsmen, we'd ask a 1st class Armourer to sign off the work but to be honest, after a couple of times, it was like riding a bike.

Now you have a backsight and a foresight that are both exactly upright and square to each other, regardless of what the parallel gauge or alignment lines say... and that's really all that's needed. Oh yes, and don't talk to me about alignment bars/lines either. If you have ever breeched up Thompson guns or SA80 rifles, then you soon learn to ignore them and do it properly. If you have any fears that the extractor slot might not align with the extractor then forget it because there is ample width to cater for it.

The same idea applied to L1A1 rifles except this time, the vee block was positioned inside the body, resting on the machined inner surface. Same with No5 rifles too but this time, because we couldn't be sure that the splayed foresight protector 'ears' were both splayed exactly, then a simple square was cramped to the parallel part of the upright that really needs no further explanation.

Now here's something that you didn't know or thought about. If you have a rifle that won't zero until the foresight it well over to the left or right, and I've seen plenty of then too... now is the time to consider whether the barrel is slightly over or under breeched. Just a slight amount will upset the balance of the foresight block...

TRX
Dec 22, 2010

I've seen the switchbarrel and benchest guys claiming torque figures from 40 to 200 ft-lb. I'd like to see someone do the latter with a couple of wrenches on a range bench...

Unless someone comes up with a better figure, I'm going to torque it to 75 ft- lb.

SavageShooter
Dec 22, 2010

Probably better to stick to 60 lb or less. The Enfield receivers are about the same diameter as the small ring Mausers and have a bit less meat to them. No sense in over stressing the receiver ring.

Alan De Enfield
Dec 23, 2010

According to E G B Reynolds in "The Lee Enfield Rifle " the barrel torque was specified at 120 +/- 5 ft lbs after there had been instances of over-torqued barrels causing bulged actions.

SavageShooter
Dec 23, 2010

I'm suprised they'd use that much torque. Then again the Whitworth thread is probably better able to handle it than a regular V thread.

Over torque of the early P14 and M1917 barrels cranked in by machine is the reason so many have cracked during rebarreling.

I'd still stick with the 65 lb as the optimum for a small ring either Enfield or Mauser.

PS
I found the section in Reynolds' Lee Enfield book that mentioned the 120 lb torque.

This was used with barrels that had been turned by .10 at the Shoulder and breeching washers used.

Those action bodies and barrels had not clocked in properly and otherwise would have required excessive force to bring them home.

The optimum breeching angle in that reference is given as 18.5 degrees.

Whether the optimum torque for barrels that did not require the washer was the same I haven't found out yet.

A custom made barrel with properly mated threads and no washer may not require so much torque.

TRX
Dec 24, 2010

I think Alan came up with the "better figure." Even if the book isn't right, it's better than me picking a number out of the air.

A thick washer, lubricated on both sides, would reduce friction as the barrel face came up against the front of the receiver, since there are two lubricated sliding faces instead of one. In some applications, a lower torque figure is specified for a joint with a washer, since less torque is needed to achieve the same clamping load. So for a barrel with no washer, you'd need to turn it in tighter. We'd probably be talking on the order of 15 or 20 ft-lb, just as a SWAG.

If I had another barrel I could cut it back .10" or so, snag a breeching washer next time I order from Numrich, and post the results. If anyone has a rusty stub or shot-out tomato stake barrel they'd care to donate to the cause, let me know.

SavageShooter
Dec 24, 2010

If I can ever get my parts bins sorted out I have a couple of stumps from SMLE barrels Which I kept for old projects still on the back burner, laying around here somewhere.

One is a section of a new or near new condition replacement barrel from breech to rear sight cross pin. The barrel had been double drilled when they mounted the sight bed and the two holes joined in a rough ditch that almost cut into the bore. I cut the barrel to be sure no one ever tried using it, and to use the section of barrel from pin to muzzle for a .32 S&W rifle project.

The other is a shot out shortened take off from a sporter. I'd planned to use it to make an adapter to hold a grinding disc to remove a few thou from the inside shoulder of a receiver ring to allow a barrel to seat further back and reduce head gap.

If you do your own machining work we might work a trade of some sort.

I have a cut down No.4 barrel taken from an unfinished sporter project started by a friend.

I figured to have it bored out to .410 and fit it to an old Lithgow action which is not restorable and probably not safe for full power rifle cartridges. The No.4 would have thicker walls if bored to .410, which would allow use of the hottest shot or slug (been planing on fabricating some aerodynamic stabilized sabotted fletchetes) handloads on brass cases.

Son
Dec 31, 2010

The above mentioned optimum breeching angle is the maintainers recommended way to do the assembly. If when installing a barrrel the angle at first face to face contact is less, then it is advised to use a shim washer to attain the 15 to nearly 20 deg considered a requirement to reach correct tension (regardless of use of washers). I have the figures here somewhere, there is an angle measurement for each of the two shim sizes (.002" and .005")

Of course the accurate "clocking" of the barrel from the >15 degree start is the aim. On some occasions it will be found that with washers fitted the correct headspace by the manufacturers specifications cannot be achieved... then either another barrel may be tried or a measured amount will be needed to be machined off both the shoulder and the breech face to clock from the 15 deg start point. Then it will require re-cutting of the extractor groove and reaming the chamber to complete the job with correct headspace.