The Treeby chain gun was a .54 caliber percussion rifle that could fire 14 rounds in rapid succession. Designed in 1854, it was unlike anything else available at the time. Only two were ever made, with the hope of receiving a contract from the British Army. The gun was tested and found wanting, and no further production was ever undertaken.
Firing the Treeby rifle requires following a specific process. First, of course, each of the 14 chambers must be loaded with powder and ball, and a percussion cap placed on the firing nipple on each one. Once the weapon is all loaded, the lever on the barrel must be rotated up. The barrel is connected to the frame by way of a very coarse thread, so lifting the barrel lever pulls the barrel forward, away from the chamber. Next, the hammer is manually cocked, which rotates the chain of chambers and indexes one into position. Then the barrel lever is rotated back down, pulling the barrel in and sealing it against the chamber. Only now can the trigger be pulled, which fires the round currently sealed up to the barrel.