|The following is based on Fallout: New Vegas cut content.|
The specifics of the heavy riveter are unknown. The weapon was at least planned at some point during development, but never made it into the final release of the game. The only remaining resource tied to the weapon is a single, unused, empty Form List, RepairNVHeavyRiveter.
The heavy riveter was not included in the final release of Fallout: New Vegas.