3d metal printing is already a reality. Of course you have to be able to afford a machine that costs (minimum) $50,000 - and that’s if you’re willing to accept sintered metal as your barrel.

CNC mills can’t make the barrel, and except for the “jewelry” level tabletops cost near or over 5 figures.

Both make better weapons, weapons that are significantly more expensive. Neither makes detector-transparent weapons.

re taggants, the experience of Switzerland shows the claim false. Note I’m referencing coded polymer, not volatile evaporants. In other words taggants that identify lot and manufacturer, not taggants to allow dogs to find hidden explosives.