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Thread: Question for Capt Laidler, indexing No.4 barrels

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  1. #11
    Really Senior Member Alan de Enfield's Avatar
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    Peters Previous Post

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    Breeching Up (post by Peter Laidler) (click here)

    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 pro’s 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 60’s Singapore…………, then if they did, I wasn’t part of the discussion!
    Last edited by Badger; 11-17-2009 at 08:45 AM. Reason: Edited for clarity ...

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    Banned Edward Horton's Avatar
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    Dear (expletive deleted) Whiterider

    It sounds like you found a crate of brand new No.4 barrels that you already had bore scoped and air gauged, and I have three questions:

    1. Did you have the barrels re-threaded and re-chambered.
    2. How many of these barrels are you going to share with your buddies here in this forum.
    3. Have you ever been blackmailed by a forum member.


    Signed
    Your best buddy Ed.

    P.S. Give my best to your other buddy Dr. Beers


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  5. #13
    Member whiterider's Avatar
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    Thread Starter

    more bloody barrel indexing...

    Okay. Having read and re-read Capt Laidlers post on the indexing of rifle barrels this is the only bit I can find on checking whether they are 'square' and 'upright' or not...

    "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."


    The information I was after was just HOW that flat plate, Vee blocks etc were used to ensure the barrel would in fact be in a position so that the foresight was mounted vertically.

    Anyway Captain, I guess I've taken up way too much of your time and thanks again for your help.

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    Regarding these washers, is the I.D. of critical importance, or just a little bit greater than the major diameter of the threads? Also is the hardness of the steel critical, will mild steel do?
    Please excuse my lack of knowledge, but this isn't just academic.

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    The washers aren't hardened, as used L1a1 spacers often show the receiver imprint on one side. I.D. isn't terribly critical either: +0.002-0.010" ought to be fine.

    As far as squaring the receiver, just run a hardened pin through the rear sight axis hole and place the outer ends in the V-block pair that are resting on your tombstone (the polished side, or use glass plate, or if you're really into spending money, a granite surface plate!) Depending on how high you can get your V-blocks you can do the rest in an upright or inverted position (the barreled action, that is, stand on your head at your own peril). Check the front sight base for perpendicularity (the sides) or parallelism (the top) to the plane of the axis pin. If you don't know how, then find some one who does!
    Last edited by jmoore; 11-19-2009 at 05:16 AM.

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    Peter Laidler's Avatar
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    Ok, ok... I'll go through it fully over the weekend. But it's a lot simpler than has been described so far and no standing on heads either!

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    Thank you! I tried to find the exact posting for this operation, but either my Computer-Fu is weak or it was on the old Joustericon forum. Pretty sure its been done before, though.

    I must admit that MY SMLE/No4 barrel swaps don't get near that "scientific", Mk1 calibrated eyeball seems to work fine so far concerning barrel indexing!

    AR15/M16 front sight/gas block replacements on the other hand are quite the fixturing opposite, esp. when trying to put new taper pins in that will match the old whilst not changing the windage zero... They demand a repeatable set-up so that the whole assembly can be removed and replaced multiple times so that pins can be driven out/in as well as swapping the sight bases themselves. Some folk say it can't be done, so I just HAD to do it- multiple times!

    BTW w/ M1/ M14icon's a precsion level is the standard barrel indexing tool.
    Last edited by jmoore; 11-20-2009 at 01:11 AM.

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    Advisory Panel Brian Dick's Avatar
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    It's so simple in fact, even I can do it properly!

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