4, New York: Press Publishing Co. (January 1894), p. 309 Intended for primarily for shipboard use against enemy naval forces in small boats, the 6mm Lee had considerably more penetrating power than the U.S. Army's .30 Army (.30-40 Krag) cartridge, and could perforate 23 inches (58 cm) of soft wood at 700 yards (640 m), a single 3/8 inch (9.5 mm) thick steel boiler plate at 100 feet , or a 0.276-in. (