8 bore

The 8 bore (Commonwealth English), also known as the 8 gauge (American English), is an obsolete caliber used commonly in the 19th-century black-powder firearms for hunting large dangerous game.

Design
An 8 bore is a .835 in caliber firearm. Historically it was used to fire solid projectiles from smoothbores, rifles, and partially rifled ball and shot guns, as well as shot from muzzle-loading and breech-loading shotguns. Later breech loaders were designed to fire cartridges.

Shot loadings
The 8 bore was a popular wildfowling calibre both in muzzleloaders and later cartridge shotguns. 8 bore cartridges were available in multiple lengths including 3-inch, 3¼-inch, 3¾-inch and 4-inch.

Solid loadings
When the Dutch established the Dutch Cape Colony in the 17th century, they soon discovered their muskets were hopelessly inadequate against local game. Within a century the most popular Boer firearm was a flintlock smoothbore musket of about 8 bore with a 5 to 6 ft barrel. Early British settlers of the Cape Colony in the 18th century also found specialist firearms were required for the local game. European gunmakers responded with various long arms from the enormous (although seldom produced) 2 bore down.

By the 19th century, the giant 4 bore had been established as the standard elephant gun amongst European settlers and explorers within Africa, whilst the 8 bore was considered the standard for all other dangerous game. Typical 8 bores weighed 15 to 16 lb, and fired a 1250 gr conical bullet at around 1500 ft/s or an 860 gr spherical ball at around 1650 ft/s, both with 10 to 12 drams (17.72 to 21.26 g) of black powder, although sometimes heavier charges of 14 drams (24.82 g) were used, generally in Africa.

In the late 19th century, William W Greener conducted the most thorough research of any gunmaker into the requirements for African hunting. After extensive testing and lengthy discussions with returned hunters and adventurers, including Sir Samuel Baker, he concluded the 8 bore was the largest practical calibre required for hunting dangerous game. Additionally, due to the increased felt recoil of rifled weapons, he recommended the 8 bore as the largest calibre for a rifle, and that firearms above 8 bore be smoothbores.

The most common 8 bore cartridges used paper cases, much like shotgun shells, and true .835 in caliber projectiles. A larger version utilising a thin brass case was also available, although it fired .875 in projectiles, in reality making it a 7 bore.

Modern uses
In modern times, the 8 bore has uses in the mining, cement, and steel industry. It has been used to knock down overhangs in mines or quarries, break up bridging or stoppages in silos, to desist boiler tubes, and remove slag deposits from rotary kilns, by blasting away at them from a safe distance. This can be done while the kiln is in operation in some instances. Various slug loadings are in production for different industrial uses. Using the C.I.P. method, the chamber pressure for the 8 bore industrial shotgun shell is 32000 psi