What is a good polygon count for a new weapon mod?

[ChokingHazard]

What is a good polygon count for a new weapon mod for Fallout 4?

 

If you have too many, it will cause severe performance issues or can even crash the game if it's extremely high, and if there are too few polygons, the weapon will not look realistic.

 

Someone on a website for the 3D-modeling program "blender" has agreed to make a Quake 2 railgun, so I need to give him some advice on an optimal polygon count for a large/heavy weapon in Fallout 4.