The most powerful naval gun

While the Yamato's 18.1 inch guns hold that distinction, it is not the biggest conceivable for the war at the time. Every major power had super battleships on the drawing board, capable of mounting improved 16-inch, 18.1 inch, or even 20-inch guns. There's the German H-44 with 8 20-inchers, the Super Yamato with 6 20-inchers.

Question: what American design could have superseded the 12 16-inchers of the Montana class BB's?

 

The US had built a couple of 18" guns prior to WWII. Testing convinced them that they had reached the point of diminishing returns. The British had even fielded a ship with a couple of 18" guns but they didn't seam all that interested in going that route either. Most of the German H class designs were merely paper studies some wouldn't have even been able to make it out of the harbors they were to be built in without significant dredging. The German 16" guns were suppose to be very good though. Indeed once it was clear just what the advantages of radar were the US might even have considered using more 16"/45s instead of 16"/50s.

 

IIRC, I read that the U.S. Navy did not wish to go much bigger than 16” guns, due to the fact that the hull design on the battleships would have to widen. That meant there would be less of a chance to get them through the Panama Canal. Has anyone else heard this, or am I making this up?

 

Our first South Dakota class, cancelled under the Washington Naval Treaty, were also going to mount twelve 16"/50s, and if it was considered necessary a modified version of that design could have been given eight 18" instead. Norman Friedman's design history of US battleships includes a concept plan of such a ship We had done a similar thing with the Tennessee and Colorado classes, transitioning from twelve 14" to eight 16".

Incidentally one of the cancelled ships was another Montana, making that the only US battleship name cancelled twice and the only state of the lower 48 never to have an active battleship named for it.

In the late 1930s the USN developed super-heavy shells including the 2700lb 16". This was considered not significantly inferior to an 18".

Eight guns were generally considered the minimum for effective gunfire control; no battleship of the dreadnought era had fewer. The six-gun Super Yamato might not have been such a good idea.

Ironically the only dreadnought-era capital ships with fewer guns were Fisher's last few battle cruisers, Renown and Repulse with six, Glorious and Courageous with four, and Furious planned to have only two. I say ironically because Fisher's big innovation with the Dreadnought had been increasing the main battery from four guns to ten.

While Yamato's 18.1"/45 were the largest guns, the British 18"/40 fired the heaviest AP shell, 3320lb vs 3219lb. Only three 18"/40s were built, mounted in Furious and the monitors General Wolfe and Lord Clive. Navweaps United Kingdom / Britain 18"/40 (45.7 cm) Mark I - NavWeaps suggests that only APC projectiles were available during WWI, so the humble monitors may have fired the heaviest shells ever used in combat.

 

I have not read that specifically, but the Montanas were going to be too wide for the canal - 121' - so an 18" ship probably would have been also.

 

No, your not making it up...with the wider 18-inch gun turrets, it was deemed that there was not enough space between the hull and magazines to provide sufficient protection from shells and torpedoes. As it was, IIRC, the distance between the hull and Iowa's magazines was deemed barely sufficient, and that of turret one was questionable.

 

As Carronade has mentioned, the US went with "super heavy" shells.

The designed super heavy shell for the WW2 cancelled US 18-inch/47 was only a few hundred pounds lighter than the Japanese 20-inch AP shell(3,850lbs vs 4,100 - 4,400 lbs).

 

Just realized I need to amend this to naval combat; on land there were the German 60cm mortar and 80cm gun.

 

proposed guns /turrets for H class twins and triples
45 cm (C42 h) and 50 cm (C42i)

 

By this you might be assuming six guns in only two turrets. Will it be different if it were three two-gun turrets?

 

I was assuming the super-Yamato to have three turrets, substituting twin 20" for triple 18.1", same sort of thing we did with the Tennessee and Colorado classes (post #4). Either way the consensus seems to have been that six guns was too few.

I've made the same comment with regard to the proposed rearmament of Scharnhorst and Gneisenau with three twin 15" in place of their triple 11".

 

The issue with 6 guns in 3 turrets is that it becomes really difficult to engage 2 targets at once. You only have 2 guns firing on one of them and with occasional non firings you may only have one gun firing at the target with on turret on it. Really difficult to correct fire. Having 3 guns on a target is quite a bit better in this regard GS did ok in that regard at River Platte. If you aren't planning on engaging more than one target at a time with your main battery 6 guns is probably ok especially if your doctrine is full salvos.

 

In the days before radar when these ships were being designed, gunnery depended on spotting the fall of shot and correcting. It was desirable to minimize the interval between salvoes, so ships generally fired half of their main armament in each salvo. Actual hits penetrating the enemy's hull were difficult to spot, so the ideal was a straddle - 1-2 shots short, 1-2 over, hopefully 1-2 hits, so 4-6-gun salvos were preferred.

 

I think US doctrine was full salvos. The half salvo thing was one reason the British proffered 4 turrets and it was their doctrine.

 

This is incomplete, and deals only with maneuvering.

More to the point
International Naval Research Organization Articles - Evolution of Battleship Gunnery in the U.S. Navy - NavWeaps

Other good articles on fire control can be found on the NavWeaps website.

www.hnsa.org also has some detailed literature on fire control in their resources section.