doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Fractionalization of bore sizes

Gentlemen, It has always been my understanding that the dividing of bore sizes into smaller portions by the use of fractions, occurred with the Proof Rules of 1887. ie 12 which previously
spanned .729-.751 was divided into 12 as .729 - .740 and 12/1 which covers .740 - .751 . I have not been able to find a confirmation of this in print via the internet. Do any of our knowledgeable throng have a definite yay or nay on this???
Thanks

Yay- I just checked into this a couple weeks ago and a member was kind enough to help me out.

OWD

I believe it was Burrard that refers to them as vulgar fractions.

Kind Regards,

Raimey
rse

The /1 fractions did indeed come into use under the rules of 1887 (and /2, for gauges 10 and larger).

Note also the /# is always larger than the gauge it is applied to. It can be calculated by simply taking the "Average" of the gauge & the next larger one & dropping all decimal points beyond three places, not rounding. If you calculate 11� gauge rounded to three decimal places you will get the same size as a 12/1 but this isn't necessarily true for all the /1 sizes as they are not true "Fractions" just an average.
For those gauges from 10 up through 3 you simply take the difference between the two gauges & split it into thirds, again dropping all numbers beyond three decimal places.

Thank you fellows. Does anyone actually have access to the 1887 Rules of Proof and the reference regarding this proofing change that was made?? I have had an ongoing discussion regarding this with someone who insists that fictionalization was adopted in 1875. I would dearly like to be able to confirm this in print once and for all....

Terry, I have the proof tables going back to 1855. They were changed in 1868, and again in 1887. No new tables came into being in 1875, and the fractions were not used in the 1868 tables. The fractions first appear in the 1887 tables.

From Baron Engelhardt's article, "Proof in Great Britain", under "Rules and Regulations of 1887":

"In all smoothbore and choke-bored barrels, from 4 to 10 bore inclusive, the bore size was divided into three parts and marked accordingly . . . from 11 bore to 17 bore inclusive, the bores were divided into 2 parts; thus the division of a 12 bore was 12 and 12/1."

I think most people accept Baron Engelhardt as perhaps the leading expert on gun proof, at least up through the rules of 1925.

Thanks Larry, that's the info I was looking for. That should end the discussion I've been having.The fact that in all the years I have handled British guns I never found one that had "Not for Ball" and fractional bore sizes,ie pre-1887, didn't seem to cut it for my friend...

That's a good observation, Terry. "Not for ball" went away when the fractions were adopted. Of course you could look at a lot of "not for ball" guns the bore diameters of which didn't fall within the fractionalized parameters. In other words, they might have really been 12's rather than 12/1, 13/1 etc. And a lot of the "not for ball" guns that were marked with fractions as a result of reproof may not have started life that way, with the change being the result of honed bores.