If you’re entering wingspan, it sounds like you’re using the funnel rather than the radar sight. The funnel is tricky, you’ll need to line up the wingspan with the edges of the funnel in the same plane of motion, pull forward a bit so the target wings are a little outside the funnel edges, then fire and relax G and let the target fly through your bullets.
Or lock them with the radar ACM modes and put the thing on the thing and fire. Much easier :)