Modern Firearms are defined by the ATF as firearms built after 1898.
Compare“Walther Arms 2844001 PDP Optic Ready 9mm Luger Caliber with 5" Barrel, 18+1 Capacity, Black Finish Picatinny Rail Frame, Serrated/Optic Cut Black Steel Slide & Performance Duty Textured Polymer Grip” has been added to the compare list