Weapon caliber

A diagram illustrating relative firearm projectile types and sizes.

The size of a firearm's bore, known as its caliber, can be defined in terms of three different units.

• The largest of Alkenstar's siege weapons, such as the Great Maw of Rovagug, can be measured in 3-inch stones (S).
• The next smaller unit is ¼-inch pebble (P), with 12 pebbles to a stone.
• Finally, a pebble constitutes 24 grains (G), the smallest unit of ballistic bore measurement.

While many personal firearm bullets are 1P in size or greater, the grain is a more common unit of measure since few of them are an even pebble in size.

Size in ...	S	P	G	Inch
Stone (S)	1	12	288	3
Pebble (P)	0.083 1/12	1	24	0.25 1/4
Grain (G)	0.003472 1/288	0.0417 1/24	1	0.010417 1/96