How about firing this pushes back the player in the opposite direction? That would make it "feel" more like a cannon shell firing compared to say rockets and other weapons. Would also give more of a reason for it to not be a "safe" or "stable" handheld weapon, and something more suited for a tank or turret. Maybe also the handheld variant to be moderately inaccurate, so you use it in a pinch but can't rely on it?

Would also give the railgun a reason to be a good upgrade late game, other than the piercing and damage uplifts of course.

What say?

That's a good idea! now I need to figure out how to do that effectively and optimized

The base game tesla turret already does that to biters, maybe there's a way to call that same method? Sorry I'd wish to help more but don't know the Factorio mod API well so just spitballing