Complex sentence: The M60 continues to be used in the 21st century by U.S. Navy SEALs and as a door gun on U.S. Army helicopters, and was the main 7.62 mm machine gun by some U.S. special operations forces to the late 1990s.
Split into simpler sentences: The M60 continues to be used in the 21st century by U.S. Navy SEALs and as a door gun on U.S. Army helicopters. It was the main 7.62 mm machine gun by some U.S. special operations forces to the late 1990s.