Editing Montana-class battleship (section)

===Initial design work===
[[File:Battleship Study - BB65 - Scheme 4 - (1940 Studies).jpg|thumb|left|1940 study plan, BB-65 Scheme 4 (BB 65-4)]]

Though the 33-knot design had been chosen for ''Iowa'', it was clear to naval leadership that these would be exceptions to normal Navy doctrine, and that a reversion to the 27-knot standard-type battleship would occur with the next design. The primary consideration for this new class was the development of the super-heavy {{convert|2700|lb|adj=on}} [[Armour-piercing ammunition|armor-piercing shell]] that had been developed during the construction of the ''North Carolina'' class. Standard design practice stated that battleships should be immune to guns of their own calibers at expected battle ranges, but the new super-heavy shell had significantly better penetrating power than older, lighter shells. None of the existing designs, from ''North Carolina'' to ''Iowa'', were proof against the 2,700-pound shell, and the General Board wanted the next design to be better protected. They requested proposals from the [[Bureau of Construction and Repair]] (C&R) that conformed to the 45,000-ton limit, armed with twelve 16-inch guns, and capable of 27-knots.{{sfn|Friedman|1985|p=329}}

C&R initially responded with a design labeled "BB 65A", which used ''South Dakota'' as a baseline, but increased the length to accommodate the fourth main battery turret. Displacement was already over the limit at {{cvt|45435|LT}}, and the ship was only protected against the earlier {{cvt|2250|lb}} AP shell. The design staff estimated that more than {{cvt|2000|LT|0}} would be needed to protect the ship against the heavier shells. A second variant, "BB 65B" substituted twelve new {{cvt|6|in|0}} /47 guns in place of the existing twenty [[5"/38 caliber gun|{{cvt|5|in|0}}/38 cal guns]] for their [[secondary armament|secondary batteries]], but this increased displacement even further. Another pair of designs, "BB 65C" and "65D", adopted three quadruple main battery turrets instead of four triple turrets, which accounted for some {{cvt|1600|LT|0}} of weight savings. This latter pair mirrored the first set in the use of 5-inch and 6-inch secondaries. All of these designs were only protected against the 2,250&nbsp;lb shell, but since "C" and "D" were below the displacement limit, C&R attempted to use the free weight to strengthen their armor with design "BB 65E". They realized that though the deck could be improved to provide a relatively narrow [[zone of immunity]] against [[plunging fire]], strengthening the [[belt armor]] to protect against the heavier shell would increase displacement to as much as {{cvt|55000|LT}}.{{sfn|Friedman|1985|p=329}}

None of the initial proposals was deemed acceptable, and there were concerns about the feasibility of the quadruple turrets. Other guns were suggested, ranging from {{cvt|18|in|0}} guns to experimental 16-inch/56 caliber guns. C&R provided another series of studies beginning with "65F". Several of these proposals experimented with mixed quadruple, triple, and double turrets for either ten or eleven guns to save weight but still increase firepower over the nine-gun ''South Dakota''s. One proposal, "65J", suggested adopting a twelve-gun {{cvt|14|in|0}} ship that would be well-protected against the 2,700&nbsp;lb AP shell. The 18-inch gun was ruled out after a design study demonstrated that only six of the guns could be mounted within the 45,000-ton displacement limit. By September 1939, one of the ten-gun variants had been selected, which carried two triple-turrets forward and a quadruple turret aft.{{sfn|Friedman|1985|pp=329–332}}