The Omaha class mixed twin six-inch turrets with casemate weapons instead of committing the whole battery to one new arrangement. That combination hedged against uncertainty over whether the experimental turret would perform as intended. Such a design is logical for one or two trial ships. Ordering a large class before proving the arrangement would repeat the experiment before its results were known.
Notable Point · 49:11-49:47
Omaha's mixed battery hedges an experimental design
The Omaha class combines new six-inch turrets with traditional casemate guns because the Navy had not yet proved the turret arrangement.