The only good filing off a serial number would do for you would be to get you locked up. Filing off a serial number is a felony. We’re surprised this is actually a common question, but of course it is. Be smart, do not try to file off a serial number on a gun. If you do, and you are caught, you will be in some serious trouble with the law. If you obtain, let’s say, an AR with a personalized serial number in it and you want to change it, contact the ATF or proper government agency to check the legality of changing it or filing it. All-in-all, don’t be dumb and file a serial number off ANY weapon.