Why large naval guns cannot be recreated quickly

Which modern industrial processes could help recreate large naval guns and armour plate?

Induction furnaces and heavy-shaft machinery offer starting points, but the necessary data, metallurgy, specialised processes, and institutional knowledge have largely faded.

Induction furnaces and machinery used for large propeller shafts might provide starting points, but neither substitutes for a lost production chain. Making a 6-inch or 155 mm gun is a different industrial scale from producing 15- or 16-inch weapons and thick armour plate. Computer modelling cannot compensate for missing test data, while tank armour and railway steel follow different metallurgical paths or work at much smaller scale. Foundry closures also removed equipment, skilled practice, and institutional memory. Recreating the capability would therefore require money, time, and fresh experimentation rather than simply retrieving old drawings.