stripped lower receiver.. with the "lower shelf "   cut OUT..    what's  the law   on this stuff...  I know the ATF website talks alot about  any part of a semi auto that takes a part  from a full auto  is illegal  stuff....   like the BCG or hammer....  so wouldn't any  "" low shelf""    receiver   be one of those parts .........over  have of the receivers out there are lower shelf   and why doesn't any of companies    posting this   as parts of the receiver,,,, they all talk about mil-spec, forged, 7075,, bla bla bla    and not one WORD about the LOWER/ UPPER      shelf......                  all my lower control group parts are fine,,, checked them ,and my BCG  all ar-15 parts only..            I guess  trying to write this   as evidence  in court    that I wasn't trying to make a non legal AR-15    is pissing  up hill and up wind...  but maybe  the judge might give me a few less years......

Receivers without a block in them or milled out in the Sear area are perfectly legal, M16 BCG's in the rifle are also perfectly legal.

The shelf doesn't matter.  

If your lower has a 3rd hole drilled for the auto-sear then ATF might have a problem.

Yup Good to go.  Just don't have "3rd hole", Full auto FCG, or a DIAS, and you are fine.

A lot of early Colt, Sendra, and I think even Bushmaster lowers were all low shelf.  (Which is a bad idea no matter what configuration your lower is in).

Current production Plum Crazy polymer lowers are also.