A small ranging gun cannot reproduce a main battery's flight

Could a long-barreled smaller gun range for a battleship's main battery?

Not reliably, because the smaller projectile lacks the range and ballistic behavior of the heavy shell at battleship engagement distances.

The idea breaks down at realistic battleship ranges. A smaller gun does not share enough ballistic characteristics with the main battery, and it often cannot reach the same distance. Observing its fall of shot would therefore not provide a trustworthy correction for the heavy shells. The tank-versus-destroyer comparison also illustrates why weapon size, range, platform movement, and rate of fire must be considered together.