Of all the gun control legislation that's been suggested over the years, the only one that appears to have had any measurable effect is background checks.
Ah, but has
it? Despite advocates' claims that it has stopped X amount of felons from buying guns, we have yet to see any negative crime trend directly attributable
There are two reasons. Actual prosecutions for violations are few and far between, and laws that aren't prosecuted generally lack teeth.
Second, criminals don't generally buy their guns from FFL's, at least not directly. They're simply not affected.
It's like attributing the AWB to a crime reduction that was already happening before it was implemented and which continued after it expired.