Here is the high poly version of my sniper rifle which I have sculpted in 3d-Coat. The 3d-Coat original file has over 45 million polygons. For fbx, blend and obj I have reduced the poly count to 8 million and 5 million, still looks like the 45 million version but the lower poly count makes it easier to work with.
Here you will find the game ready version with pbr textures: https://www.cgtrader.com/3d-models/weapon-military/gun/sniper-rifle-ksr-29