https://www.rockislandauction.com/detail/69/3218

Wall guns are the philosophical predecessor to today's anti-material rifles - large-caliber, high power rifles heavy enough that they cannot be fired from the shoulder realistically. Traditionally, they were used for defending walls or ramparts, as the name implies. They would allow defenders to perforate armor that would be proof against normal shoulder rifles, and also have a more substantial ballistic impact at long ranges than a normal rifle.

This particular one was made in Belgium in 1862, and is a .75 caliber breechloading design with a percussion ignition and hexagonal Whitworth-type rifling.

http://www.patreon.com/ForgottenWeapons