I was there in 1967, in Malaya at first with 4 RAR when we saw our first AR15 rifles. There was only a provisional training pamphlet and no EMEI's either. The ARr15's has a pxxx poor reputation that was following them around. We didn't have a lot of ammo or spare parts that had to come down from Butterworth or up from Singapore Ordnance. They slowly replaced the old Owens (supposedly....) and the new issue F1's. I went to Australiashortly afterwards and there were only a few AR15's around then. Feel free to correct me on the date-line. I flew back to Malaya and immediately went on a 'get-to-grips-with-this-PDQ' course at 40 Base Workshop, the Far East Training Centre with RAEME Armourers Johnny Cotterell, John Dudley, Lauri Taggart and a pommy Armourer called Dave Lee for a crash course on the AR15's that we had to take with us!!!. To be honest, by then, we knew more about them than the instructors. But we got through it - and got HIM through it too!
We incorporated some worthwhile modifications during the course. A while we started to get the first M-16's and later, the M-16's with the thumb-close mech. Johnny Cottterel went to Bandiana to give the RAEME training school instructors a crash course - the blind leading the blind. It all worked out and afterwards, we realised that this was going to be our jungle rifle as sare parts and ammo were coming in and the old shotguns and SMG's were going OUT. By the time the Poms (the KSLI) were withdrawing, the M16was the norm and the KSLI M-16's replaced out old AR15's. The open flash eliminator was a xxxxxxx nightmare in the jungle
Much later, the M-60 GPMG was falling out of favour, especially by those instructors at Singleton who had got to know about the L7/FN MAG58 GPMG - , better known as 'THE GENERAL'. So I had a bit of fame because I'd been taught the L7 in theory but not the practice so was able to pass on a few of its magnificent features. I have to say that compared with our M-60's of the time, they were chalk and cheese
So, back to AR15's and M-16's. I say, 1967 we saw them and by mid to late '68 the early M-16's were on stream - followed by the later models in 1969
Please feel free to correct, alter or add as it's 50+ years now