Besides providing increased velocity and a flatter trajectory, the primary reason for the change in cartridge and bullet design was to reduce chamber pressures and extend the life of the rifle barrel: the new 112-grain loading with its copper-jacketed bullet gave an average barrel life of 10,000 rounds as opposed to only 3,000 for the 135-grain steel-jacketed load. Ordnance authorities specified a slightly slower rifling twist for the new loading – one turn in 7.5 inches (18 cm). At some point during later production, this rifling was again changed to one turn in 10 inches RH (25 cm). The U.S. 6mm Lee Navy (6mm U.S.N.) cartridge used by the U.S. Navy and Marine Corps was initially supplied by Winchester Repeating Arms (WRA) and later, the Union Metallic Cartridge Company (UMC). The rifle powder was Rifleite, a nitrocellulose flake powder supplied by a British company, the Smokeless Powder Co. Ltd. The cartridge was semi-rimmed, and was designed to function in machine guns such as the M1895 Colt–Browning as well as in infantry rifles. Intended 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 , or a 0.276-in. (7 mm) plate of chromium steel (no backing) at 150 feet. Another advantage to the 6mm cartridge was in the reduced weight of the ammunition: 220 6mm cartridges weighed approximately the same as 160 cartridges in .30 Army caliber. The basic combat ammunition load of an 1898 naval bluejacket or marine was 180 rounds of 6mm ammunition packed five-round clips, and carried in black leather ammunition pouches. Outfitted in this manner, a navy bluejacket or marine could carry considerably more ammunition than that of the typical Army trooper of the day, who usually carried 100 rounds of .30 Army ammunition in individual cartridge loops on his Mills canvas cartridge belt. However, the 6mm U.S.N. cartridge may have been too advanced a concept for the technology of the day. The Navy experienced continued problems with the Rifleite smokeless powder used in the cartridge, which appears to have varied in consistency from lot to lot, while becoming unstable over time. These problems were exacerbated by the custom of keeping ammunition aboard