Lion-class battleship guns and turret design

Would the Lion class have reused Nelson-class guns and turrets?

No. It was planned with improved 16-inch guns and new turrets derived from, but not identical to, Nelson practice.

The planned 16-inch gun was a new and improved design rather than a reuse of Nelson's weapon. It was intended to offer a possible upgrade path for the Nelson class as well. The turrets drew on Nelson experience but did not simply copy the installed mountings. Designers returned toward the original heavier turret concept after attempts to lighten it had produced the opposite result.