ArmaLite rifle, any of several lightweight, small-caliber assault rifles designed by the American manufacturer ArmaLite, Inc. The first ArmaLite rifle, the AR-10, was a 7.62-millimetre, gas-operated weapon with a length of 40.5 inches (102.9 cm) and a weight of 8.8 pounds (4.0 kg). It did not survive its trials but did pave the way for highly successful similar designs, notably the AR-15, the U.S. Army rifle designated as the M16. ArmaLite’s AR-18 rifle resembled and operated like the AR-15, but it was carefully redesigned to be easily manufactured with unsophisticated equipment in less-developed countries—although no such arrangement was actually made.