Japanese 14-inch shells and British 13.5-inch quality

Would Japanese 14-inch shells have been better than Royal Navy 13.5-inch shells at Jutland?

Probably not by much: the guns and shell designs came through closely related British firms and tolerances, while Japanese manufacture still drew on recently imported British skills.

The shells were likely to have broadly similar quality, with no decisive Japanese advantage. The guns and ammunition designs came from closely connected British industrial sources and were made to comparable tolerances. Although production took place in Japan, the manufacturing knowledge had only recently been imported from Britain. Projectile performance depended on this industrial lineage as well as caliber.