The .30-06 Springfield cartridge (pronounced "thirty-aught-six" or "thirty-oh-six"), 7.62×63mm in metric notation and called ".30 Gov't '06" by Winchester, was introduced to the United States Army in 1906 and later standardized; it remained in use until the early 1980s. The ".30" refers to the caliber of the bullet, and the "06" refers to the year the cartridge was adopted—1906. It replaced the .30-03, 6mm Lee Navy, and .30-40 Krag cartridges. (The .30-40 Krag is also called the .30 U.S., .30 Army, or .30 Government.) The .30-06 remained the U.S. Army's primary rifle and machine gun cartridge for nearly 50 years before being replaced by the 7.62×51mm NATO (commercial .308 Winchester) and 5.56×45mm NATO, both of which remain in current U.S. and NATO service. It remains a very popular sporting round, with ammunition produced by all major manufacturers.