The Pancor Jackhammer was a select-fire combat shotgun designed by John Anderson in the 1980s. He was a Korean War veteran who had used a pump shotgun in combat, and while he liked the shotgun concept, he felt there must be a more efficient way to make a shotgun than a single-loading pump action. The tinkered with ideas and designs, and ultimately devised the Jackhammer. It is a remarkably clever and interesting mechanism, combining mechanical elements from the Mannlicher 1894, 1895 Nagant revolver, and the Webley-Fosbery automatic revolver.

After making several dozen mockups out of wood and clay to get the mechanics just right, Andersen built a fully functional prototype, which is the gun you see here. It used a lot of large cast parts (and weighed a fully 17.5 pounds), and had a very slow reloading process. However, it proved that the concept was valid and it worked reliably. Anderson then made two more with much lighter materials and a much improved reloading mechanism. These two guns were submitted to the US military for testing, and both were ultimately destroyed by HP White Labs in destructive tests. The testing proved very positive (the guns survived a 50,000 round endurance test), but were ultimately rejected by the military.

The first prototype was kept personally by Anderson, and is now the sole existing Jackhammer. It was owned for several years by Movie Gun Services, which rented it to a number of film, video game, and comic book companies. Because of this and its very distinctive appearance, the Jackhammer has made appearances in a vast number of comics and video games.