In 2008, Taser release the X12, a Mossberg 500 shotgun modified to use a miniaturized Taser cartridge called the XREP (eXtended Range Electronic Projectile). The idea was to create a Taser system that could be effective in the intermediate range (30-100 feet) where a regular handheld Taser could not reach, but from which thrown projectiles could still be a viable threat against someone.
Where a normal Taser fires two barbs tethered to the unit (which holds the battery and completes the electrical circuit), the XREP had to be fully self contained to have the desired range. So the electronics package and battery were scaled down and shock-proofed, and the payload divided into two parts connected by about 12 inches of wire. The front part would hit with 4 barbs, and then the rear part would swing around and impact elsewhere on the person, completing the circuit and initiating a 20 second pulse. One of those wires was left uninsulated, so that if a person tried to grab them to pull the projectile off, that action would itself complete the circuit.
The shotgun used was a Mossberg 500, but fitted with a crossbolt safety like an 870. It was also given a special proprietary bolt face which would not function with regular 12ga ammunition. The XREP cartridges were cut to fit this bolt face, and this ensured that one could not accidentally load lethal ammunition into the X12 shotgun. It also used a rifled barrel, with a fast 1:18″ twist to properly stabilize the XREP. Ultimately, the project was a commercial failure, primarily because of the cost of the cartridges. At something like $125 each, they were nearly five times the cost of regular Taser ammunition.
Thanks to Deviant Ollam for the loan of the gun!