The SWATriplex-18 was a bullpup dual-fed shotgun designed by John W. Winter in the late 1970s. It was semi-automatic and incorporated twin tubular magazines.
The design was unsuccessful and the SWATriplex-18 was not mass-produced. It is thought that the main reason for the SWATriplex-18's failure was that it was too far ahead of its time, and that many companies thought that it looked too strange.
However, the modern Kel-Tec KSG shotgun incorporated some of the SWATriplex-18's features, and has been far more successful.
The SWATriplex-18 is a semi-bullpup shotgun using dual magazine tubes beneath a singular barrel. The weapon can be fed from one of the tubes at a time, or alternatively between both tubes. It is a gas-operated, semiautomatic weapon with a telescoping bolt. The SWATriplex-18 is constructed of a combination of light alloys and steel, especially for the 22-inch barrel where strength was critical.
The barrel and tubes are surrounded by a shroud/hand guard that is ventilated for cooling. The weapon also features ejection ports on both sides of it, and each could be sealed to allow usage by both left- and right-handed shooters by reversing the ejection direction, charging handle, and cheek rest.
The weapon uses rifle-type sights on raised stands that are adjustable for elevation and windage via knobs. This design element was thought of as being a potential problem, with Winter himself considering on either removable sights or positioning the sights down to the receiver.
The stock is made of a light alloy, boasting a synthetic butt with a rubber recoil pad.
On top of the receiver is a carrying handle that could be folded flat against it if desired by the user.