I've had some of the same experience as dlb. I just ask them 'What's this registry you're talking about? Explain it to me'
ETA: Although I think here in NJ there is some registry, at least at the local level, on handguns. We need a permit to purchase a handgun, and it's a 4-part carbon copy form. At least one of the copies gets sent to the local PD. (I'll have to check my paper work later when I get a chance).