Originally Posted by gunsmoke11
Apparently you weren't around back then and have much to learn, but I can assure you that Colt was the AR15 that was around with perhaps the Costa Mesa AR18, if you're familiar with it. I have no idea where your info comes from, but I suggest you rethink it. When those parts from the M16 were placed into the Colt AR15 the auto sear was just slipped in. No talent of any sort was required, as was proved by the morons caught doing it and there were many.
Actually yes I was around then, hung out at my friends place, a gun shop and he was one of the (and still is) best gunsmiths I have ever known,and he taught me a lot just by being there and helping out when he needed extra help, and I was paid (heck I would have done it for free) in gun stuff
A little history from someone that was there... They changed the receiver what was it... I believe back in the late 60's early 70's (civilian versions were referred to as AN-15 military was M-16) on all the platforms in the civilian world so they would no longer accept the drop in select fire sear.
Early civilian AR's were made that way for a reason... It was rumored that If the military had an emergency need they could simply hit the civilian stock piles, at least that was in the gun rags of the time.... (sorry no INTERNET or home computers then, other than the ALTAR 8080 that is, you had to go to a book store and buy a magazine to read). and then the 1968 gun law hit home....
Over the years there have been multiple changes on the lower, and upper, mostly to lighten, make them easer to manufacture, added the jam clearance, better triggers, improved bolts, gas system improvements, but as far as I know new parts will fit older AR's but the auto sear in anything not an AN platform NOPE, not with out some major work and modifications.