The P-12 was an American prototype shotgun that was designed by Monolith Arms.
The P-12 was a concept developed by Brian Abbott, controller of "Monolith Arms", in about 2005. The gun was brought to public attention in 2008, when Abbott released a marketing video onto the internet showcasing a prototype model, but did not explain the gun's operation or show it being fired. This led some observers to believe that the P-12 was a non-functional mock-up and that no working prototype existed. As of yet, the P-12 has not reached production stages and there have been no further developments on the design.
Abbott himself later claimed that an unspecified manufacturer (likely Magpul) expressed interest in the P-12 and bought the prototype, but ultimately chose not to put it into production, as they felt the design was not in keeping with their brand image. The sole prototype allegedly remains in their possession to this day.
The P-12 was a pump-action shotgun that utilized a top-mounted horizontal magazine, similar to that of the FN P90. According to the designer, the gun was built from a mixture of 3D-printed and store-bought components, the latter to allow for easy repairs if replacement parts were needed. The weapon was planned to feature an adjustable trigger weight.