People who commit violence out of ideological devotion may rise to the level of competence required to assemble weapons from over the counter components. It alr

People who commit violence out of ideological devotion may rise to the level of competence required to assemble weapons from over the counter components. It already happens occasionally, like with the 2005 London bombings. I very much doubt that the typical gun toting criminal of today will rise to that level of competence. I wouldn't expect the median member of the law abiding public to successfully make a rifled firearm and ammunition given a machine shop, a shed full of agricultural chemicals, and a year to practice. My expectations are even lower for the median armed criminal. Most will get distracted or injure themselves before reaching success. I don't think that a cottage industry of weapons-for-criminals is going to spring up in the same way as illicit drug production. The drug trade is nearly impossible to vanquish because so much of it is victimless; neither the seller nor the consumer attracts much attention in the usual case. But if you're dealing weapons specifically to people who can't get them by legal means, that's much riskier. Most would-be attackers who meet with a "bomb seller" are actually meeting with LEO. The novelty factor of "3D printed" firearms leads to law enforcement worrying about them disproportionately to their actual significance. They're mostly an exotic hobby.