Rifled muzzle loader

In contrast to smooth bore cannon which preceded it, the rifling of the gun barrel allowed much greater accuracy and penetration as the spin induced to the shell gave it directional stability.

This new gun and the rifled breech loader (RBL) generated a huge arms race in the late 19th century, with rapid advances in fortifications and ironclad warships.

Other navies, notably France, continued to develop and deploy RBLs, but they were hardly superior in rate of fire or muzzle energy to their British counterparts.

During this period rapid burning black powder was used as the propellant, and the guns had a stubby, 'soda bottle' shape giving easy access to either end for loading.

A catastrophic accident on board HMS Thunderer in January 1879, in which a 35-ton 12-inch muzzle-loader hung fire (misfired) and was subsequently double-loaded, killing eleven sailors, motivated the Admiralty to re-consider the RBL.