So if you should want - and I would never recommend such a thing - a fully 3D printed firearm... Those would be illegal to transfer, naturally, but you can make something like that for yourself legally if you should be so inclined and naturally I would never entertain the notion myself. Officer.
Guns are not going to help in the next conflict. You better print drones of all kinds. drones with hunter killer AI on board GPU means no need for remote guidance and makes them unjammable only EMP can fry them and that’s not something joe six pack will ever have. AI drones of the flying kind all sizes, cat or rat sized quadrupeds to scurry into buildings and rubble or tunnels, even down to wasp sized winged drones.
5 grams of TNT or RDX from two feet away is 100% lethal in overpressure even without shrapnel. A wasp sized drone could carry 5g. You don’t even need high brilliance materials. Biologicals are even lighter for lethality. The lethal dose of fentanal is in the micrograms range a hypo stinger with that would be lethal in seconds. Same for VX or any of the CNS agents. Even commercial bug spray in a hypo stinger would be lethal in gram amounts. Drones can mist a room with an agent then just fly or scurry out. Mist CNS don’t need to be breathed skin contact with micrograms mist amounts is enough. Does the resistance have MOP4 suits and could they fight in them 24/7.
Drones can be armed with projectile weapons that fling RDX or TNT filled fragment rounds from a distance with supersonic speeds well outside shotgun ranges. Ask the ukes and Russians both sides have fully automatic weapons there is video of guys emptying a full AK74 mag as a drone and it still kamikaze dives into them and BOOM no more guy with a fully automatic weapon.
Drones and mechanical engineering is the next war or conflict it’s silly to think having a 16th century device will turn the tide or win that conflict. Those who control the tech win the next war and war.