An elephant gun is a large caliber gun, rifled or smoothbore, originally developed for use by big-game hunters for elephant and other large game. Elephant guns were black powder muzzle-loaders at first, then black powder express rifles, then later used smokeless powder cartridges.
Theodore Roosevelt with a Holland & Holland double rifle in .500/450 Nitro and bagged elephant.
CZ 550 .585 caliber rifle
A gun is a device designed to propel a projectile using pressure or explosive force. The projectiles are typically solid, but can also be pressurized liquid, or gas. Solid projectiles may be free-flying or tethered. A large-caliber gun is also called a cannon.
SIG Pro semi-automatic pistol
Battleship USS Iowa fires a full broadside from its nine sixteen-inch naval guns
A 'flying-cloud thunderclap-eruptor,' a proto-gun firing thunderclap bombs, from the Huolongjing.
The first firearm (a "proto-gun"), the fire lance, from the Huolongjing.