Could a 45-calibre 20-inch naval gun have been built then?

Could a 45-calibre 20-inch naval gun have been built in the period under discussion?

A proven, useful service weapon remained beyond period capability. Factories could expand their equipment, but barrel metallurgy, droop, turret weight, ammunition handling, and rate of fire made the proposed gun substantially less credible than an 18-inch weapon.

The answer separates apparent factory constraints from the harder limits of gun design. The comparison applies to capital-ship projects such as HMS Incomparable and large Japanese designs. Larger cranes and quenching wells were achievable, but they did not solve barrel construction, safe operation, ship balance, or useful combat performance. Without the treaty interruption, or with battleship development continuing into the 1950s, sustained British-American competition might eventually have produced the required breakthrough. Nine 18-inch guns therefore appear more plausible than six 20-inch guns, and the 20-inch proposal remains a development ambition instead of a ready service weapon.