$35 MK18 Assault Rifle Low-poly 3D model by DamianMinnie. Available on CGTrader with 127502 polys and 655 vertices. Check it out on CGHub.
BLEND (Blender, filesize: 287 MB), OBJ (OBJ, filesize: 11.3 MB), FBX (Autodesk FBX, filesize: 4.47 MB), PNG (PNG, filesize: 1.02 GB)