TexasCHLforum.com

Most ARs have the serial number on the magwell. If people are willing to break the law, they can drill out the serial number and half an inch around it without affecting functionality at all. Drill or grind all the way through and there is no way to raise the number from metal that doesn't exist. If they're real hard cases, they can ambush cops and take their guns. That's much less work than making a ghost gun.