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Draw lapped on the inside and possibly draw filed on the outside? It's surely what one would expect to see- having done the same procedure a few times on different things. Could also be a minor vibration from turning the OD with insufficient support. Oddly, that sort of pattern is quite common on wartime production M1911 pistol barrels. The directionality of the tooling marks will tell the story.Quote:
Originally Posted by Thunderbox
That was one of the pictures I was looking for, If you have a round barrel resting on two hardened steel flat bars and then strike it like the illustration then you will get the marks in line with the bore! Just try it! If the Barrel was resting one the sharp edge of the blocks the marks go the other way.
Just before I spring a bit of info into the ring regarding barrel straightening, had anyone got photographic or other evidence of No4 (or 5) barrels being straightened? Because we don't think that they were. The round billets were deep gun-bore drilled and an 8" 'GAUGE, TESTING, STRAIGHTNESS OF BORE'; was passed through. If this passed, then the bore was straight enough for the wartime semi skilled barrel viewers. If it wasn't straight then production was so fast and automated that the barrel was scrap and put back in the melt. It was machined/rifled etc to the bore to keep them concentric. You can't straighten No4 barrels with a dolly-mallet due to their thickness. ...... you have to use a roller press and only Bren barrels were straightened on presses due to their weight and complex machining. But even then, Bren barrel bores (presumably straightened ones.....) were notorious for being eccentric and I showed a photo of a cut one recently that was truly, visibl;y eccentric. But it shot OK until the day I cut it in half
That's just what we were told and I stand to be corrected.
Maybe No5 barrels COULD be corrected using a dolly mallet as they were thinner and light - I don't know - but if deep bore drilling was accurate enough for No4 barrels, then I suspect that No5 barrel failure rates were minimal. But, as I said, this is just what we were taught about barrels during our barrel viewing phase and even had the 8" gauge.
Can anyone come up with anything, such as pictures or other evidence of production No4 barrels being straightened?
This picture shows what appear to be no4 barrels being straightened or "setting" as the caption says!
Yep, that's all the convincing that I need. It just goes to show that what you took in all those years ago isn't necessarily correct. I can only assume that those barrrels are being set after being rifled and after the long straightness gauge has failed to run.
Mind you, I think he'd need a bigger dolly mallet than that to rectify a No4 barrel or lump it pretty hard!
Thanks XL39