 A heavy barrel version, known as the "FAP" ("Fusil Automático Pesado", or heavy automatic rifle) was also produced for the armed forces, to be used as a squad automatic weapon.The Argentine 'heavy barrel' FAL, also used by several other nations, was found to frequently experience a failure to feed after firing two rounds from a full magazine when in automatic mode.A version of the FALMP III chambered in the 5.56×45mm NATO cartridge was developed in the early 1980s.