Why a French high-velocity 13-inch gun is not a simple upgrade

What would France need to build a high-velocity 13-inch gun with quad turrets and autoloading for a Dunkerque-type ship?

It would require rebuilding the gun-development and production system, developing suitable long barrels and materials, and solving an exceptionally difficult heavy-gun autoloader problem.

The proposed weapon would exceed what French industry could reliably deliver in the interwar period. France would have to redesign how it developed and manufactured naval guns rather than enlarge an existing weapon. Making the design viable would require competing development teams or institutions of excellence, together with a wire-and-steel barrel strong enough for a very long 60-calibre weapon. The autoloader presents a separate challenge because even much smaller six- and eight-inch systems remained difficult decades later. The battery would therefore demand a whole industrial and research programme.