What gun records? Feds are (supposedly) prohibited from keeping them, but the states may be doing it. Chances of the gun being bought in Maryland or Virgina are practically nil I'd imagine. Unless they have the gun, or at least the model, it's an impossible task. They'd have to check all sales of all .223 caliber guns. Just the AR-15s and clones would take forever...unless they are all on a computer somewhere. Doing it the legal way, going the manufacturers and working down though the wholesalers and retailers is probably more than just a bit impractical (and we want to keep it that way too!).