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TABLE OF SHOT GUN OR SMOOTH-BORE GAUGES. 
In days of old, before arms were rifled, missiles were round and shot from 
a barrel that was smooth-bore like a shotgun ; the gauge or calibre was num¬ 
bered according to the quantity of a perfect sphere of lead there was contained 
in a pound. Thus, 50-gauge rifle was bored for a ball that took fifty of them 
to weigh a pound, 20-ga. twenty to the pound, 16, 14, 12, 10, etc. The adjoin¬ 
ing table reduces the standard shotgun or smooth-bore gauge decimally to thou¬ 
sandths of an inch, also to millimetres. 
Diameter in decimals of the inch. 
Gauge or bore. 
Diameter millimetres. 
•835 
8 
21-8 
*775 
10 
20*0 
•726 
12 
18*6 
•693 
14 
17*8 
*662 
16 
16-8 
•615 
20 
15-6 
*571 
25 
14*4 
•537 
30 
13*6 
•526 
32 
132 
•488 
40 
12*4 
*453 
50 
11-4 
