Regarding your comment in whether or not members support the concept of a NICS check....
I suspect the vast majority of us have no problem with a NICS check in concept - that is, a simple check to see if a potential purchaser is on a list of prohibited persons (lots of assumptions here... just for the sake of this argument assume the only way you get ON this list is by being convicted of a felony, that due process was followed prior to your conviction, that an actual procedure exists to have your name removed from the list if it's been placed there in error, etc.).
What we (well, I at least) DO have a problem with is the requirement that the 4473 form created to facilitate that NICS check be kept readily accessible for 20 years, and be made available to the ATF upon request. Although it requires a lot more leg-work to "query the database," this is still, in effect, a national firearms registry. THAT's why these 80% kits are so popular among members of this board. It's not that we object to a background check. It's that we object to the paper trail it creates. It hasn't been discussed much yet in this thread, but this proposed rule change also proposes changing that 20 year requirement to, in effect, forever. Maybe gangs are building 80% kits now... I would have to think their tried-and-true methods theft and straw-purchases by girlfriends, newer gang members without records, etc., would be a whole lot less work though. The point is, nobody HERE wants to build 80% lowers to get around a background check. They want to build 80% lowers so that if/when confiscation occurs, there's no record of those builds.
I do understand from the previous thread (discussing the original leaked draft of this proposed rule) that the primary reason for running serial number traces is not crime solving, but checking recovered guns (often in an effort to return them to their original owners). But I still don't think a registry is a good idea given the global history of gun control, and the trajectory of it in this country.