 These wire-wound built-up guns had originally been planned for the cancelled G3-class battlecruiser design upon which the "Nelson" class drew.Sir W. G. Armstrong Whitworth & Company at Elswick, Vickers at Barrow-in-Furness, William Beardmore & Company at Dalmuir and the Royal Gun Factory at Woolwich made a total of 29 guns of which 18 would be required for both ships at any time.These guns broke with the example offered by the earlier 15-inch Mk I gun, which fired a heavy shell at a rather low muzzle velocity, and instead fired a rather light shell at a high muzzle velocity; this was not a success, as at the initial muzzle velocity the gun wore down rapidly and the accuracy was unsatisfactory, so much that it was lowered.