6 bore
The 6 bore, also known as the 6 gauge, is an obsolete caliber that was used commonly in 19th-century black-powder firearms. == Design == 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.