Toby Obermeit shows the new RMR30 Carbine at the Shot Show in Las Vegas Kel-Tec extensively used 3D printing to prototype the new RMR30 carbine, a .22 Magnum that uses the same magazines as the PMR-30 pistol. The carbine has a retractable stock, a 16 inch barrel, and uses a straight blowback action, instead of the delayed blowback of the PMR-30 pistol. The RMR30 required a redesign of almost the entire firearm, even though the magazines are interchangeable. Here is a view of the RMR30 lower receiver alongside a PMR-30 pistol. The changes were prototyped with 3D printing. As...