Estimated barrel lives for longer 15-inch guns

What barrel life was expected for the 15-inch/50 and the proposed 15-inch/58?

About 320 rounds is given for the 15-inch/50. Around 200 is suggested for the 15-inch/58, but that second figure is an estimate without a written design figure.

The question starts from a remembered figure of roughly 400-500 rounds per lining for a 15-inch/42 gun. The corresponding figure for the 15-inch/50 is given as about 320 rounds. A possible 15-inch/58 is estimated at around 200 rounds, with an explicit warning that no written estimate is available for that design. At such a short life, firing a full ammunition load could bring a ship close to needing new linings. D-Day bombardment provides the operational comparison: ships could return after repeated ammunition loads needing barrel work while they reloaded.