( 250 ) 
In comparison to calibre of rifled arms, it will be observed there is a 
marked difference; in this table, as the size of the gauge increases, the numerals 
designating the diameter of it decrease. Thus, the size of the hole in the 
barrel of a 25-gauge smooth-bore is '571, while for 50-gauge smooth-bore, it is 
only ‘453. For a rifle barrel of exactly ’25 Cal., the bore should be *250; for a 
'50 Cal., it would be i inch or 500. The calibre or gauge of the modern rifled 
arm, if correct, is designated decimally by hundredths. Thus '32 Cal. should 
be 32—100, '40 Cal., 40—100, etc., though few of them are really what they are 
called. We would remark here that the round ball for shotgun, as cast in Eng¬ 
lish moulds, is about fifteen thousandths ( - 015) smaller in diameter than figures 
designated in the table, allowing for the thickness of the patch. 
HOW TO FIND OUT THE TWIST OF RIFLING. 
Lubricate the inside of the barrel well. Take a bullet that is large enough 
to fit snugly so as to get a full impression of the rifling. Force it through the 
barrel carefully. Get a piece of straight wire smaller than the bore of the rifle; 
drill a hole in the bullet and fasten one end of the wire to it; shove the bullet 
with the wire fastened to it from the muzzle to the commencement of the rifling 
at the chamber. Fasten the barrel in a vice or otherwise : make a chalk mark 
