ya know, i've wanted to ask that question (convictions from the 94 bill) myself FOREVER but thought it had already been beaten to death on here.
i personally haven't heard of a case yet.
i have to admit, i look at my pre bans that i paid waaaaay too much for and think that with my laid back shooting habbits, & my-not even having a parking ticket, angelic ass-, what kind of situation would i ever get into that would require somebody looking into verification of one of my AR's? and even a more simpler & realistic scenario, what LEO carries the "serial number" list? a good chunk of LE probably have no clue when it comes to the ins & outs of the 94 crime bill. i mean, we know all of it, we have to. plus we're law abiding folks (for the most part) and want to do the right thing.
but THE MILLION $ QUESTION is (with all what i just said in mind) what real problems am i ever going to encounter if i decided i wanted to try a pre ban upper at the range for an hour, or for that matter, for the week long shooting trip?