Small-bore refers to calibers with a diameter of .32 inches or smaller.[1] It may also refer to small-bore rifle competition. The medium-bore refers to calibers with a diameter between .33 inches up to .39 inches and large-bore refers to calibers with a diameter of .40 inches or larger.[2] Miniature bore refers historically to calibers of .22 inches or smaller.
There is much variance in the use of the term small-bore which over the years has changed considerably with anything under .577 caliber considered small-bore prior to the mid-19th century.[3]
Small-bore competition often refers to shooting competitions conducted with .22 Rimfire target rifles.[4][5]