"The Proof House is the "shooting gallery" of Uncle Sam's St. Louis Ordnance Plant, one of the World's largest producers of machine-gun and rifle ammunition. For twenty-four hours a day dunners fire anti-tank gun, browning automatic rifles, garands and every other military weapon to test the .30 and .50 caliber ammunition produced by the Big Plant. The St. Louis Ordnance Plant is operated by the United States Cartridge Company."