Why heavy naval guns were difficult to manufacture

What limited heavy naval-gun production, and could it be accelerated?

The metallurgy and repeated forming process were inherently demanding; only more, preferably protected, facilities could materially increase output.

Large gun barrels sat near the technological frontier of the 1920s and 1930s. Their steel had to survive pressures exceeding many armor applications, while repeated heating, rolling, and final rifling demanded unusually exact work. The process itself offered few safe shortcuts. Production could be accelerated chiefly by adding specialized facilities and protecting them from bombing, so industrial redundancy mattered as much as nominal factory capacity.