BR25199 U.S. Tanker with M3 Grease Gun

Despite efforts to simplify its design, the M1A1 Thompson submachine gun was still a time-consuming and expensive gun to manufacture. Research and development of a cost effective alternative resulted in the M3 “Grease Gun.” Produced by the General Motor’s Guide Lamp Division, it was a stamped, sheet-metal surrogate for the primarily milled Thompson. With its riveted and welded construction, the M3 was originally designed as a disposable small arm, to be used and then discarded once it became inoperative. This simple weapon permitted the installation of a conversion kit – a replacement bolt and barrel, recoil springs, and a magazine adapter would change the weapon’s original .45 caliber to that of 9 mm Parabellum.