I'm curious how they propose to prevent that as a credit card company needs to know which card was used for a purchase as they have to bill the owner and also the merchant that they have to pay. Couple that with the fact nearly every place I've purchased firearms from have pretty obvious names like "Buds Guns" or "Palmetto State Armory" and you they'll have a pretty decent idea of who has probably been buying guns or at least probably owns them based on that.

And thanks to the ATF mandatory paperwork if the Government wants to know if my $649 purchase from Buds Guns was a gun send the ATF to inspect the records (and yeah, I know that Buds transfer record would be to another FFL generally and not me specifically, but all the paperwork forms a trail that is easy to follow back to the FFL I would have picked up from).