MtMan-List: Re Gauge conversion.

["Pat Quilter" <pat_quilter@qscaudio.com>]

                      Re Gauge conversion. 
Dave Kanger asked about a "gauge" to caliber conversion for a spreadsheet. The
classic explanation is that "gauge" is the number of balls per pound for the
exact bore diameter (normally, of course, you actually load with slightly
smaller balls). If we know the balls per pound for any given ball diamter, ie 12
gauge = 0.725 inches, then any other caliber can be found by cubing the ratio
between the known gauge and the unknown. For instance, a 45 caliber barrel would
have a "gauge" of 12 times (.725/.45) cubed, or 12 x 4.182 = 50.18. Note again,
that the actual balls one would load would be slightly smaller hence 52-53 per lb.

   The spreadsheet operator for exponents is the carat ^. The cube formula is
=(value)^3. (Cube roots use -3).  Then you will need a benchmark ball diameter
vs weight. I once bought 10 lbs worth of .690 balls which came out to 147, so
this diameter measures 14.7 balls per pound. Just to check, lets take the cube of
the ratio of actual bore diameter to .690, ie,  (0.725/.690)^3 yields a ratio of
1.16; dividing into 14.7 balls/lb =  12.67 balls/lb at 0.725", which is still
not exactly 12. So either my bore is not quite standard or the weight vs count
was a little off.  I encourage you to obtain a more accurate benchmark with your
own data, but the spreadsheet formula should be:
CELL 1: benchmark gauge (ie 12):
CELL 2: benchmark diameter (ie, .725).
CELL 3: new diameter (ie .45)
CELL 4: new gauge, = CELL 1 * (CELL 2/CELL 3)^3 
Apologies to the brethren for this non-historical computer lingo. Hope this
helps Dave. 
yr Ob't S'vt 
Pat Quilter