The Pancor Jackhammer was developed by American gunsmith John Andersen as an automatic repeat-fire shotgun. The design was patented in 1987 with development work under the Pancor Industries brand label of New Mexico. The Jackhammer intended to combine the hard-hitting lethality of the 12-gauage shell with the repeat-fire nature of an automatic weapon, utilizing a revolver-style approach. The end product became a large - if cumbersome - futuristic-looking weapon that never found any takers on the world stage. Pancor Industries went into bankruptcy and all company assets - including the Jackhammer prototypes and plans - were sold off. The Jackhammer Mark 3 was the last known derivative of the Jackhammer design and it is estimated that no more than three were ever completed. For a time, the Jackhammer was being evaluated by the United States military which prevented its sale to foreign parties and, thusly, this added to the weapon's demise.
At its core, the Jackhammer was a conventional gas-operated system which allowed for full-automatic fire from a revolving 10-round ammo-cassette feeding 12-gauge (2.75") shells in through the rear of the receiver. The weapon sported conventional iron sites and two integral loops to serve as carrying handles across the top of the receiver. The barrel featured a distinctly angled muzzle cap with the angled pistol grip integrated into the underside of the weapon body. The Jackhammer weighed 4.57 kilograms with an overall length of 787mm and barrel length of 525mm. The firing action was semi-automatic or full-automatic through a selector switch. Rate-of-fire was listed at an impressive 240 rounds per minute. Due it its high rate-of-fire, the National Firearms Act of 1934 in the United States categorized the Jackhammer as a "machine gun" due to its high quantity repeat-fire capabilities, subsequently resulting in heavy regulation.