Originally Posted by bgeddes
Doesn't the lower have to be machined for the 'special' parts to be able to function?
The subtles between a basic "AR" and an "M16" lower are quite small really. Yes, there are some "extra" machine steps that are needed, but there are, well, pretty basic.
Zes - If what you say is true, you need to get the unit checked out by a professional. If you have an illegally modified AR lower - you are looking at quite a stay at Club Fed just for the possession of said lower.