Staff Writer (Updated: 8/9/2016):
Despite its futuristic appearance and dual-function fire mode, design of the SPAS-12 was somewhat conventional as a whole. The shoulder stock (detachable wooden, synthetic or folding metal) was appropriately set at the rear behind the pistol-type grip with the trigger system protected by an oblong ring. The receiver was mostly rectangular in shape with clean straight lines throughout and sported the cartridge ejection port along the right hand side. Perhaps the forend hand guard / slide of the SPAS-12 was its most identifiable design element, wrapping around the tube magazine fitted underneath the barrel. Shells were inserted into the tube magazine one behind the other. Sights were optional as were muzzle accessories, broadening the tactical scope of the weapon. General iron sighting was accomplished by a rear aperture and front blade arrangement. Beyond standard slug and spread rounds common to shotguns, the SPAS-12 could also "fire less-than-lethal" ammunition for the purposes of riot control - hence its interest by security parties. While fitted with an integrated lever safety, issues with the system resulted in a product recall.
There were few variations in the SPAS-12 production line and early forms were actually completed with a wooden fully detachable stock but this eventually gave way to the more common folding metal version. A synthetic stock was also later offered. The metal version could also be fitted with an optional folding underarm "loop" for improved single-handed firing - though this was always thought as impractical to most, considering the sheer weight and recoil of the weapon. The SPAS-12 family could subsequently be found sporting between 18- and 24-inch barrel systems and ammunition counts ranging from 5-, 6- and 8-rounds.
The SPAS-12 attempted to break the civilian sporting gun market but the system ultimately proved too unwieldy and generally complex for big game hunting or competition and the shotgun was eventually outlawed from import in the United States for its very "militaristic" features (high ammunition count, semi-automatic fire mode, heat shield for sustained firing, etc...). With the American gun market out of reach and global interest limited, Franchi ended production of their SPAS-12 in 2000. However, the lessons learned in its design and development went on to forge the later SPAS-15 series of automatic shotguns.
In the military market, the Franchi SPAS-12 found a home with Austria's EKO Cobra counter-terrorism units. Similarly, Indonesia fielded the SPAS-12 with their Komando Pasukan Katak and Komando Pasukan Khusus special warfare groups. Malaysia assigned the shotgun to their Special Operations Force and Bangladesh purchased the weapon in quantity for their Presidential Special Security Force. In the United States, SWAT teams were given access to the SPAS-12 for a time but the shotgun never found a permanent military home with the American military.
Incidentally, the acronym used to designate the SPAS-12 stood for "Sporting Purpose Automatic Shotgun", this being something of a psychological effort on the part of Franchi S.p.A. to help counter import bans and other restrictions arising within several countries by making the gun appear as more of a "sporting" system than the obvious. Regardless of its limitations and reach, the SPAS-12 went on to become one of the most recognizable shotguns in history.