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

**Peter Laidler** · 11-20-2009 01:42 PM

ON THE SQUARE
As a result of a request from forumers, I’m going to tell you how WE, the REME Armourers breeched up No4 and 5 rifles. And while we’re at it, this is the principle of how we did L1A1’s 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…………..

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