An old bolt action rifle crudely converted to steampower, it has been assembled using spare scrap metal found lying around junk heaps. The stock houses 2 detachable gas canisters that are needed to give that extra power in the field, at the end there is a heavy lump of steel to take the majority of impact from the monsterus recoil, or alternatively it could be used as a last resort after you find yourself surrounded by foes without any ammunition.
rendered in blender cycles.
model: https://sketchfab.com/3d-models/sr1-rifle-be99121a994d4fbfbb8cd5084891143a