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"The Enfield inch" when an inch is not an inch!
Just brought this and had a quick read very interesting and explains allot of why things are the way they are and the Pratt & Whitney connection worth getting, probably cheaper on kindle if you are not into books.
Peter may be able to expound on why the issue was not really admitted to but oh boy I wish I had one of those first pattern rifles sent over with the sealed drawings. :p
You can learn something every day!
- Whether or not it's useful depends on your needs :D
There are (or rather were) inches and inches...Like Hanoverian inches, Viennese inches etc.
It's not just academic. I have a Hanoverian muzzle-loader rifle and a Viennese revolver. Both made to inch dimensions. In mm the sizes are weird. For instance, the barrel length of my M. 70/74 Gasser revolver is 184.4 mm - very odd - or 7.26" (imperial) - no it's not supposed to be 7-1/4"!
In fact, it is 7.000 VIENNESE INCHES.
Of course, you need to know that the Viennese inch (used until 1871) was 26,3401mm. Divided into 12 lines of 2.195mm. Which in their turn were divided into 12 points of 0.182917mm.
Armed with this knowledge, a pocket calculator, and a bit of patience, the oddball cylinder diameter of 48.32mm becomes a straightforward 1inch 10 lines - Viennese!
Fortunately, mid-19th C. European gunmakers appear to have used mostly Whitworth threads, at least for serious items like breech plugs and barrel threads. This was, of course, before the Americans had a bad attack of the "not invented here" syndrome and came up with Sellers threads to confuse the rest of the world.
So with a discrepancy of only 0.0003 between the Enfield and imperial inches, I reckon you Enfield types have it easy!