So one of my passions is WW2 era theory crafting; what if we continued building fighting machines in a simplistic WW2 style but with modern production methods ? My latest pipe dream is a very large battleship intended for long range shore bombardment. My question is would it be possible to get a 4400 lb solid core 18 inch gun round up to 1500 m/s ? Now correct me if I’m wrong but a longer barrel generally equates to a higher velocity, so if we have a 18"/70 cal. that would give us a barrel length of just over 105 feet. I think anything longer that that would be incredibly impractical and prone to incredible wear. Another concept I thought about was the use of multiple propellant charges (sort of like the V3 gun but with just one very large secondary charge just forward of the firing chamber.) Any thoughts at all would be appreciated !