Two different vehicle designs were designed for the XM800 project, Lockheed's XM800W unconventional articulated 6 × 6 wheeled armored car and FMC's XM800T tracked version. Both models initially featured the same turret with the US-built version of the Hispano-Suiza HS.820 20 mm autocannon, the M139, as the primary weapon, as well as a M60-derived machine gun on a pintle mount. The M139 had been selected for all of the MICV projects. The XM800W was later equipped with a new turret design that kept the M139 cannon, but that had an upper cover that flipped forward to form a gun shield, or rearward to close up.