If the hypothetical gun can reach the target, the drone only needs to find it and report its position. The aircraft could then be smaller than a drone carrying its own attack payload. The suggested minimum is a camera, a communications link, and enough aircraft to carry them. The shell would deliver the strike after the observer called for fire.
Notable Point · 3:19:34-3:20:15
Small drones spotting for very long-range guns
A heavy gun with sufficient reach changes what the supporting drone needs to carry.