So this came about when I stuck three sensor upgrades on a marksman rifle mech to see what would happen. Answer: not what I expected.
What I was expecting was the shaded white range band to increase in size (which I assume corresponds to the “optimal range” stat), but this didn’t change at all - instead the thin white min/max ranges bands (where “weapon effectiveness” drops to 50%) moved instead. I don’t know about other players, but I barely pay attention to these; the stated weapon effectiveness drops off so fast outside the white zone that I always try to keep my targets in it - and that’s what I wanted the upgrades to do.
Now I get that presumably making the min/max range wider makes the weapon effectiveness (what does that mean anyway?) drop off less rapidly outside of the white band, although I couldn’t really test it consistently, but I feel it should improve the optimal range as well - even if it’s to a lesser degree.