doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Reilly .500 BPE Hammer gun for sale

Miller, can you go through the math steps, slowly please, to say convert a .729" bore to gauge using your 1.669285 factor. Thanks

Daryl;
No problem. I will write it out in formula form with;
1 = diameter of a 1 gauge @ 1.669258".
D = diameter.
G = gauge.
� = cubed.
3√ = cube root.
/ = over or divide by

The formula for finding the gauge for a given diameter is then;
G = 1� / D�
Thus to substitute numbers;
Gauge = 1.669285 cubed / .729 cubed = 12

To find the diameter of a given gauge the formula becomes;
D = 3� (1� / G).

The 1.669285 is a critical dimension for this to fit the entire range of sizes given in the English proof tables. It can vary only on the 6th decimal place & only by a couple of numbers, but the 5 is close to the middle. I worked this number out using a programmable calculator so could just put in one figure & hit run, made it a lot easier.

I went canoeing one afternoon after work & had the calculator in my pocket. Capsized the canoe & drowned it & never replaced it. It is very simple to do on an ordinary calculator though & I virtually always have one handy. Old habits die hard, even though I have been retired now for going on 20 years I am seldom found without a calculator, 6" flexible machinist scale & a steel tape measure (YoYo) at hand.

If you have any further questions on this please ask.

The double rifle sold for about $3,800, not a bad price for a .500 BPE. It looks good in the ad but Caveat Emptor.

Re-reading the ad though, it shows that the seller at least read the Reilly line on this board before writing it...simply because, unlike every previous ad I've ever read, including the two previous efforts to sell this gun, this seller got the dates of the Reilly shop at rue Scribe, Paris right (1868-85). He also mentioned both Reilly proclivity for excellent walnut in his stocks and the tight rose engraving. The seller, Commonwealth Arms, still called the firm "enigmatic" though... Maybe with a bit more research, they can stop using that word.

That was not a bad price for this .500 BPE Double Rifle. I think it probably would have sold for a higher price if the seller didn't have the reputation they have acquired. The questionable return policy and 10% restocking fee... if a return was even approved... certainly got my attention.

I want to thank Miller for providing that formula for converting Gauge to Caliber, and vice versa. I've saved it and bookmarked it for future reference.

Miller, many thanks. Daryl

Let me make one thing clear. This is all based on the geometrical fact that spheres are proportional to the cube of their diameters. Obviously, when the British made their proof charts giving the diameters of the various gauges they used this formula. The 1 gauge diameter was rounded off to three places, so listed as 1.699" on the charts. If one simply uses 1.669" as the base it will result in some very slight errors while going through the entire chart. The only part I played in this was to just set down & calculate the exact number was needed for the 1 gauge to make all gauges fit the existing chart. As I said you Must go with 1.66928x, & I now do not recall exactly how much that X can vary, but 5 works out & is convenient to remember. When working with either a calculator or a Keypad on a computer after putting in the 1.669 & moving to the center 285 is bottom, top &, middle numbers.