<P> This was the first M16 variant adopted operationally, originally by the U.S. Air Force . It was equipped with triangular handguards, butt stocks without a compartment for the storage of a cleaning kit, a three - pronged flash suppressor, full auto, and no forward assist . Bolt carriers were originally chrome plated and slick - sided, lacking forward assist notches . Later, the chrome plated carriers were dropped in favor of Army issued notched and parkerized carriers though the interior portion of the bolt carrier is still chrome - lined . The Air Force continued to operate these weapons until around 2001, at which time the Air Force converted all of its M16s to the M16A2 configuration . </P> <P> The M16 was also adopted by the British SAS, who used it during the Falklands War . </P> <P> The U.S. Army XM16E1 was essentially the same weapon as the M16 with the addition of a forward assist and corresponding notches in the bolt carrier . The M16A1 was the finalized production model in 1967 . </P> <P> To address issues raised by the XM16E1's testing cycle, a closed, bird - cage flash suppressor replaced the XM16E1's three - pronged flash suppressor which caught on twigs and leaves . Various other changes were made after numerous problems in the field . Cleaning kits were developed and issued while barrels with chrome - plated chambers and later fully lined bores were introduced . </P>

When was the forward assist added to the m16