[oldenuff2no]

you are right and wrong in this. I should have qualified that in this area there are no full auto black guns around. They have been illegal for decades.
There is a difference in all of the newer AR and M-16 receivers but I’ll send that in private.

Thanks

[Red Steel]

If you milled a lower receiver you can. However, I mentioned above about a Drop in Auto Sear, which I should have placed more emphasis. See video.

http://www.youtube.com/watch?v=jdR7rEuLrvE

From the youtube video description - verbatim in quotes:

Which "they are an excellent investment and can legally turn any AR15 into a select fire "M16" here in the good ol' USA. "

The legal ones are registered so they sell for a premium.