M16 Rifle Low-poly 3D model is available on CGTrader for $29. Original author: UltiRealm. Specs: 55471 polys, 43795 verts.
BLEND (Blender, filesize: 1.46 GB), OBJ (OBJ, filesize: 4.73 MB), FBX (Autodesk FBX, filesize: 2.56 MB), TEXTURES (Textures, filesize: 4.35 GB)