A derivative of AR-15 rifle by Arsenal 205th, Combined Service Command, Ministry of Defense, Republic of China that still has not been fully destroyed by communists on the island formerly known as Formosa, also known as Taiwan today. The design was based on AR-15, due to some butt-headed generals who said so, but the some other not-so-butt-headed generals recognized that the ball powder produced by Arsenal 203nd, under the same dominion , not only doesn't deliver enough chamber pressure, also produces hell lot of carbon and otherwise corrosive shit, so they ordered AR-18's piston to be installed instead of copying the original direct-inject mechanism. Thus the Type 65 Assault Rifle was born. Colt couldn't sue them because they have modified the gun so much, even with slight re-designed trigger group, to actually became another gun, an really ugly but otherwise lasting and effective weapon often seen in the hands of Noriega's thugs and Haitian mobs. T65K2 is the second improvement of the original Type 65. The letter T was in place of "Type" to designate indigenously made small weapons. Carrying handle was put back as mount for TS72, or newer TS85 NVG, which are roughly equivalent to 1st and 2nd generation NVG used by US armed forces, made by Factory 402nd, the same dominion. The mount was designed by idiots or conscripts and often loses parts during field maneuver. It is incompatible with anything designed for AR-15. The trigger group was further re-design of original trigger, with safe, full, burst and single options. Surprisingly, the trigger design is actually better than M-16. There is no forward assists in all T65 family, and it is not needed. It is basically a well-functioning weapon despite some design glitches. Though some design features, such as gas tube, handguard and sight mount are clumsy or simply joke, at least it shoots properly most of the time, and requires less maintenance than M16.
Do not change parts of new, shiny, good-looking and fancy T91 rifle's bolt assembly to old, grease, but otherwise well-functioning T65K2. They are not compatible.