Check out Tank Capolla Machine Gun Design 3D model on CGTrader for $2. High-quality mesh by r-kennedysydney. Animated.
STL (Stereolithography, filesize: 85 MB), OBJ (OBJ, filesize: 128 MB), BLEND (Blender, filesize: 145 MB), FBX (Autodesk FBX, filesize: 69.3 MB)