Gun parts Free 3D model is available on CGTrader for free. Original author: tobyvankempen.
STL (Stereolithography, filesize: 695 KB), OBJ (OBJ, filesize: 542 KB), 3DS (3D Studio, filesize: 134 KB), DAE (Collada, filesize: 990 KB), FBX (Autodesk FBX, filesize: 880 KB), IGE (IGES, filesize: 299 Bytes), MAX (Autodesk 3ds Max, filesize: 277 KB), SKP (Sketchup, filesize: 333 KB), OTHER (Other, filesize: 121 KB)