When a stand fires small arms against anything that is not infantry (i.e. vehicles and structures) use the OV value. Likewise, when a stand fires small arms against infantry use the FP value.
Now you mention range.
When you target a vehicle or structure remember the sequence used. You have to hit then if the "To-Hit" roll is successful then you roll for damage on the Kill Table. The "To-Hit" calculation has several modifiers (including range) to determine the final number to roll.
When you target an infantry stand there is no "To-Hit" roll. You use the "Fire Power" (FP) number at the appropriate range and then go directly to the Kill Table (apply modifiers) to roll damage.
So range is accounted for when you used either the OV (vs vehicles or structures) OR FP (vs Infantry)
Review the Kill Table chapter (P 8.1) specifically the Attacks vs Infantry and Attacks vs Guns sections to understand the differences and read play examples.
Hope this helps.