The diameter of the bore, as a cannon or other firearm, or of any tube; or the weight or size of the projectile which a firearm will carry;
as, an 8 inch gun, a 12-pounder, a 44 caliber. [
1913 Webster]
" The caliber of firearms is expressed in various ways. Cannon are often designated by the weight of a solid spherical shot that will fit the bore; as, a 12-pounder; pieces of ordnance that project shell or hollow shot are designated by the diameter of their bore; as, a 12 inch mortar or a 14 inch shell gun; small arms are designated by hundredths of an inch expressed decimally; as, a rifle of .44 inch caliber."
[1913 Webster]
"The caliber of empty tubes."
[1913 Webster]
"A battery composed of three guns of small caliber."
[1913 Webster]