Something along the lines of RFID? I've heard them described as "radio controlled" before too. Since it's in the chamber protecting it from external sources of

Something along the lines of RFID? I've heard them described as "radio controlled" before too. Since it's in the chamber protecting it from external sources of interference / attack (e.g. programmed to explode at the end of the muzzle) should be easy to protect against physically. I guess you could do it with some mechanically retractable pins or something, but electrical contacts and the inside of a bullet chamber don't seem like the sort of thing that should go together to me. You'd need to clean them constantly.