M61 75mm A.P.C. Projectile
In October 1940 Ordnance standardized M61 w/BDF as THE armor piercing projectile for the 75mm gun. But delays with production of the base detonating fuze forced loading plants to assemble it with a steel base plug instead. These were painted black (instead of olive drab) as they left the arsenals. Mass production began in 1941. Production gradually shifted to M61 w/BDF as fuze production allowed. In 1943, better designs for attaching the ballistic cap were approved culminating in the standardized M61A1. These gradually replaced M61 on the production lines. Also in 1942, a shift from aluminum ballistic caps to steel began, resulting in an estimated savings of 4500 tons of aluminum in 1943 alone.
Assembly/loading plants or arsenals completed the A.P. round with:
M18 75mm Cartridge Case