"Thumper" was a Swedish concept...
reviewed by Col. Cooper in the October, 1980 edition of Soldier of Fortune magazine. The gun, which only existed in a couple of prototypes in caliber .221 Fireball and Cooper's preferred caliber of .44 AutoMag, was the design of Bertil Johansson, of Malmo Sweden, an employee of the (then Swedish-based) AimPoint company. The gun had an in-the-grip magazine, folding stock, and came with an 11 or 16" barrel and compensator. It looked a lot like a Terry carbine, and a bit like an Uzi. It was envisioned as a cop piece, hence the nomenclature of the design: PC80, for 'Police Carbine, 1980'. Like the Scout and the 10mm D&D pistol, the Colonel's idea was a hard sell, and the idea died aborning. He tries to resurrect it every few years...most notably in TRSS&STT.