I'm not sure if these stats are kept anywhere. In PA, these stats may be kept by local sheriffs or chiefs of police, but I could not find any statewide info. I have found in PA, that 606,924 firearms were purchased/transferred in 2011 and 12,510 guns were used in violent crimes in 2011. Of course there are a bunch of variables here, this doesn't mean all 12,000 guns used in crime this year were purchased this year, or actually purchased at all, among other things. This is about as close as I can get to numbers here without a whole lot of research.
Ray