[oldenuff2no]

The drop in auto sear works about the same as a LL. But we are talking apples and oranges. It does not make an AR an M-16 it just convert the AR to full auto without selective fire.
As I said all modern AR receivers have the pin holes in a different location than the modern M-16’s do. The spacing is different and I believe one of the pins is larger. You can not take a M-16 parts kit and put it in an AR receiver and make it work without filling in the pin holes, using a template and re-drilling the holes. The same goes the other way around too. The parts kits do not interchange.

[Red Steel]

The bottom line here is that you can turn any AR15 into a select fire weapon.

[Red Steel]

You can not take a M-16 parts kit and put it in an AR receiver and make it work without filling in the pin holes, using a template and re-drilling the holes. The same goes the other way around too.

Have you ever heard of an "80% lower receiver"?

An 80% lower is not a fully built AR receiver and therefore has no serial number. It is just a hunk of metal in the eyes of the law so it is legal.

You drill your own original holes yourself and build the gun.