You presume that relatively soft plastics are the only things you can print. Remember that there are strong ceramics and metal alloys that can be easily powder

You presume that relatively soft plastics are the only things you can print. Remember that there are strong ceramics and metal alloys that can be easily powder-printed or laser-sintered. There are also strong plastics and epoxies that can be produced through various curing processes that can be performed on the same level of detail as other printing techniques. And I can imagine a gun design where a disposable/replaceable receiver and/or barrel can be designed out of weak materials and mass-produced. You also presume that recoil impact will hurt your hand. There exist a number of gun designs that minimize recoil impact by increasing the motion of the gun or relocate/reorient the barrel to minimize the motion of the gun. See, for example, any women's purse pistol, palm pistols, or a Rhino revolver.