Here is the high poly version of my rail gun design which I have sculpted in 3d-Coat. The 3d-Coat original file has over 50 million polygons. For fbx, blend and obj I have reduced the poly count to 8 million and 4 million, still looks like the 50 Million version but the lower poly count makes it easier to work with.
Here you will find the lowpoly version: https://www.cgtrader.com/3d-models/weapon-military/gun/rail-gun
OBJ (OBJ, filesize: 196 MB), 3B (3D Coat, filesize: 456 MB), BLEND (Blender, filesize: 283 MB), FBX (Autodesk FBX, filesize: 256 MB)