A triple 9.2in/50 turret

I am probably the only person in the world interested in this, but I calculate the barbette diameter give the caliber of the gun and the number of barrels per turret. For the triple 9.2in/50 turret, the barbette diameter would be 26.6ft (rounded). I always figure that 60% of the barrel protrudes from the turret face, so in this case, the guns would protrude 23ft.