Myron, about reply 123, which implies the question why the M-16 and it's variants have lasted so long in service.
The US fought only one war where the fighters spent a lot of time "in the mud" with the M-16, and that was in an area with a lot of short ranged shooting, where the M-16 does very well. Most of the reliability complaints also date from that theater.
Since then, we've been able to supply most of the fighters with a secure area for make and mend, and cleaning the M-16. The M-16 would have been replaced long ago had the troops been forced to use it some place like Korea where they had to stay out in the mud and shoot long distances. (If I recall correctly, those special forces that do spend a lot of time in the field generally do not use any of the M-16 family on their little camping trips.)
We have also replaced long range shooting with artillery, air support, and armed drones, and we had to do that because of both the M-16's range limitations and the lack of target spotting and shooting ability of recruits that did not hunt as children.
People ask "Why is the M-16 so popular with so many armies if it has so many problems?" Well, the US gave them away to all those countries, leaving the money they would normally have spent on rifles available for more important purposes, like booze, drugs, and whores for the people ruling those countries. Of course they like those free guns.