During the Vietnam war era, as a newly graduated mechanical engineer, I was hired by Colt's Firearms, the original manufacturer of the M-16, and tasked with M-16 related assignments during my employment.
There was no commercially available civilian version of the AR-15 prior to the U.S. Military's decision to make it the default military rifle replacing the M-14, and designating it as the M16A1. I have significant personal experience with the issues experienced by the M16A1, which were the result of a combined civilian/military screw-up. [JF note: this screwup was the subject of my original article.]
The AR-15 was developed specifically as a military weapon to replace the M-14. It was probably one of the first major weapons systems to be privately developed following the DOD's decision to privatize the design and development function. This function had heretofore been carried out by publicly funded government operations, most notably, in the case of military small arms, the Springield Arsenal.
The AR-15 derived from a design by Eugene Stoner. His original design using that architecture and operating system was the AR-10, which used the 7.62mm NATO round. Seen today, it looks like an overgrown AR-15. The Armalite Company tasked two engineers with developing a version of the AR-10 that used the 5.56mm cartridge; these engineers were Jim Sullivan and Bob Fremont.
Only after civilian manufacturers like Colt's made boatloads of money producing M16A1's and selling them to the government did someone (I believe it was Colt's Firearms) decide to make and sell a semi-automatic-only version of the weapon for civilian sale. It was, of course, known as the AR-15.
Small but significant changes were made to the architecture of the lower receiver, primarily slight relocation of pivot pins and redesign of the trigger/hammer components that pivoted on them, so that it would not be possible to acquire, legally or illegally, M16 trigger/hammer and fire selector components and thus easily convert the AR-15 to possess the same full automatic capability as the M16.
***
Like Eugene Stoner, whose mission was producing better equipment for the military, I do not believe that there is any place in the civil
