| Harmonica gun or Slide gun is the term used to describe a form of percussion firearm which was breech loaded with a steel slide, containing a number of chambers bored in it. Each chamber contained a separate primer, powder charge, and projectile . The slide was inserted in an opening in the breech action and could be advanced laterally to bring a fresh round into place - either by means of a lever, or simply by cocking the hammer.
The most famous maker of Harmonica guns was Jonathan Browning, father of John Moses Browning. Commencing in 1834 in Quincy, Illinois, he began to make Harmonica guns and more conventional revolving rifles. He continued to improve on the principle after his conversion to Mormonism and emigration to Nauvoo, Illinois, and finally Ogden, Utah.
One of John Browning's slide guns is on display in the John Browning home and gun shop museum in Nauvoo, pictured below.