The Machine Gun ban was one line or so out of several pages of the law. It was a literally last minute amendment. It was never debated in the House, and there are only a couple of lines in the Congressional Record that mention it in the Senate debates over the bill. It's not clear if President Reagan even knew it was in the bill when he signed it.
But there was lots of good stuff in the bill. A "right to transport" provsion aimed at states which ban a particular gun or require a license for possession from enforcing those laws against people merely transporting guns through their jurisdiction. A removal of the record keeping requirement for purchase of "handgun ammunition" (I remember using my military ID to purchase a few boxes of .22 short that I put through my wife's grandfather's little Browning rifle). Restoration of the ability to purchase ammunition interstate (ie mail order), and host of other things.
For a good, if a bit "legalistic" and "historic" discussion of the FOPA of 1986 see "THE FIREARMS OWNERS' PROTECTION ACT: A HISTORICAL AND LEGAL PERSPECTIVE" by David T. Hardy[*] .
The amendment failed a voice vote, but was declared to have passed anyway. Demands from some on the floor that it be put to a recorded vote were ignored.
Unfortunately, we didn't have the Internet back then. Most people didn't even know about that provision until after the bill was signed.
Thanks for the info.