Enfield Barrel Drawings?

[Nailcreek]

Thanks Gents for posting. I've sent a request to the Lithgow museum, but haven't heard back. While I understand that he could take the dimensions off the take-off barrel I supplied, my concern is that if he uses one barrel, well ... you have the dimensions from one barrel. I've no idea how close the barrel is to the factory spec, hence my interest in getting drawings over to him. At least then, the barrel is almost "new old stock", so to speak.

[Bruce_in_Oz]

if you are making a SMLE barrel, there are a couple of things to keep in mind:

The taper is straightforward; the challenge is turning and finishing a long, flexible tube without excessive vibration. The final finish was originally done by grinding.

The thread can be cut conventionally with a single-point tool, or you can go wild, grind a fancy milling cutter and do it in your trusty Bridgeport with the fancy gearbox gizmo attachment..

The thread IS qualified; HOWEVER, if you profile the exterior but ignore the "driving flat" on the Knox form, you can cut the thread by the technique of your choice.

The trick is to then machine the flat AFTER fitting, ditto the slot for the front sight block/band. That way it SHOULD all end up square.

As for fitting the rear sight base; even in the factory there appears to have been an "allowance" for "adjusting" the barrel exterior so that the sight base fitted without distorting the barrel or the base.

Because the factories had the tools AND gauges, they could supply barrels already fitted with front and rear sights as spares for armourers.

The location of the extractor slot and the feed ramp in the rear of the tenon can be marked out during "hand" fitting and then machined. Note that the extractor slot is radiused to match the form of the ectractor.

Remember that SMLEs breech up on the REAR of the tenon, not on the shoulder. The rear of the tenon is also the face from which headspace for the rimmed .303 is gauged.

[Paul S.]

... he could take the dimensions off the take-off barrel I supplied, my concern is that if he uses one barrel, well ... you have the dimensions from one barrel. I've no idea how close the barrel is to the factory spec, hence my interest in getting drawings over to him. ...

Bruce's reply above offers the best information from the machinist's perspective - and you have to love it when a true professional speaks.

Looking at your problem historically from a draughting perspective, current geometric dimensioning and tolerancing is a comparatively recent innovation. The first nationally coded draughting standard, BS308 didn't come into effect until 1927! From all evidence, early 20th century mass-production manufacturing depended very much upon either 'try and fit' or hand-fit. That meant you had a box full of parts 'A' and another box full of parts 'B', etc. You'd take a part 'A' and try parts 'B' until one fit. The odd bits were set aside and hand-fitted if need be. That said, using a new made component produced using nominal dimensions would be essentially what occurred at least until the middle of WWII.

[Peter Laidler]

Bruce in Oz and Paul S hit the nail straight on the head........ The No4 AND the No2 revolver were classic examples of what we call 'selective fitting' - as were Webley revolvers too. A good example was that some new No4 barrels were extremely tight in the action you were re-barrelling and there was simply no chance of screwing it in by hand to start. On the other hand, some were so loose it was like throwing a sausage down the main street! And don't even get me started about fitting new factory toleranced parts into No2 revolvers.........

Bruce mentions the nocks form or breeching up flat against the indexed barrel thread. You should NEVER rely on this breeching up flat to align anything other than...., well, nothing! I have seen that flat used to align barrels using the gauge supplied (as opposed to the Armourers own gauges/flat plate) and the foresight block has been visibly canted over.......