The 6 bore is a .919 in (23.3 mm) caliber firearm, used both as a shotgun firing shot and solid projectiles from muzzleloaders and breech loaders, both in smoothbore and rifled long guns.
A 6 bore cartridge rifle built by W.W. Greener in 1891 for a southern African trekker called Viljoen, fired 1,750 gr (113 g) bullets at 1,550 to 1,600 ft/s (470 to 490 m/s).
While designed to fire shot, experiences with dangerous game in Africa and India led to them also being loaded with solid projectiles.
[2] By the 1850s, the ivory trade was well developed in Africa and India, and muzzle loaded 6 bores were relatively popular, particularly for rifled weapons as opposed to smoothbores.
[1] Sir Samuel Baker had a 6 bore made as his first specialist elephant rifle.