Check out M16A2 Gordon Carbine Low-poly 3D model on CGTrader for $45. High-quality mesh by MirrorChaos: 54801 polys, 55399 vertices. PBR, Textured, UV Mapped.
OBJ (OBJ, filesize: 29.9 MB), MA (Autodesk Maya, filesize: 36.3 MB), FBX (Autodesk FBX, filesize: 6.44 MB)