Chrysler tank arsenal. Testing is through at the proving grounds adjoining the Chrysler tank arsenal, near Detroit. This is one of the twenty-eight ton M-3 tanks, the steel monsters which will make our mechanized forces the equal of any in the world in tank warfare. The lower of the two barrels is that of a 75 mm warfare gun, the upper of a 47 mm. anti-aircraft gun, both standard equipment on these tanks. In addition, four machine guns are mounted on each M-3