I don't know much about the following web site but I thought I would pass it on. http://www.hotgunz.com/
I had a Springfield M1 Garand (Danish) SN 3389927 and M44 Mossberg SN150337 stolen out of the back of my van on 11/10/01. Report was filed with the Newark, Ca Police.
The problem with serial numbers is there are many different versions of serial numbers. Japanese rifles might have the same serial number as listed as stolen but of a different series. Same with many other serial numbers with prefix letters. Unless that series or prefix letter is completey listed on the stolen report, it can come back to a different gun. Ray
I have a son in law in law enforcement..so I have him run numbers on occasion to see what info is available.
Most important thing is keeping a serial number list and description of your arms. If the guns are stolen..you have something to report besides "My 870 got stolen..it had a 30 inch barrel and pretty wood"..this is precisely what happened to a coworker of mine..I sold him the shotgun..I had bought it from another coworker and sold it to the coworker from whom it got stolen...nobody(me included) bothered to record the serial number..the gun had come from a hardware store that no longer sold guns..so they had no records either. So that 870 is probably still out there..stolen..but not listed as stolen.
I imagine a large number of guns floating around the market are 'hot'..but no way to trace them to particular previous owner.