The /65 means that the gun length is 65 times the caliber, or 6500 mm. That’s over 21 feet long. I don’t know if this refers to just the barrel length or the entire gun.
The Iowas main guns were 16"/50 which is 800 inches, or 66.667 feet!
Thanks!
Given that this is the “IMHO” forum, I’ll come right out and say that clever had nothing to do with it. They were slow, damaged themselves almost as much as the enemy when firing a broadside, tended to be pushed off course by the wind acting on the “sail”, and were butt-ugly to boot. The Richelius did the all-forward main battery much more effectively and were 7 knots faster.
It was renown before that. badum tsh
Four points: a) the Richelieus were over the Washington Treaty limit, something the Nelsons avoided; b) you’re exaggerating a number of the downsides (the self-damage appears to be apocryphal); c) I personally think they look quite clean and interesting, not ugly at all; d) we said cool, not brilliant. 
I’ve always liked the South Dakotas. I mean here are some ships that are nearly as capable as the Iowas and yet were put out on about 25% less displacement. They had 16" guns and the 20 5" guns, the same belt armor, and the same 3cm radar fire control systems. Obviously the real drawback was speed being about 27 knots to the Iowas’ 33-34.
To me this was one of the great engineering feats of the time. Take a ship and make something like this on a (nominally) 35,000 ton displacement? That is a piece of engineering. Nothing like having an artificial limit imposed on you to get the creative juices flowing.
One of the two Nelson class BBs (I think it was Rodney) hods an unusal distinction. Since the Nelsons could elevate their main batteries much higher than normal (40 degrees iirc), a design feature to take advantage of plunging fire against weaker deck armors, the Rodney (I think it was her) was able to elevate and fire the 16-inch main battery at approaching Italian aircraft.
They didn’t get any hits. But after the 16-inch freight trains bored through the middle of the squadron, the Italian pilots understandably diverted to a different objective.
IIRC that’s the largest-caliber shells ever fired at aircraft.
I always thought the Fuso was pretty cool looking with the pagoda forecastle
For battleships, caliber means length of gun barrel, as a multiple of the bore.
100mm (bore) * 65 (caliber) = a 100 mm gun with a barrel length of 6500mm.
Why does barrel length matter? Generally speaking, a longer barrel will mean a higher muzzle velocity (assuming you are using the same propellent charge), which translates to greater range, accuracy, and penetrating power.
One of the trade offs for having a lighter displacement was that they were a bit cramped (by American standards), if I remember correctly.
The coolest battleship I ever worked with was a stealthy one. By the book, it didn’t really offer much in way of movement; but under the command of those that scoffed at those rules, it could silently move about the ocean. Opponents everywhere would be stunned when they learned that despite hitting the target a first time, nary another nearby shot would land. Alas, it only took 4 shots before she’d sink. The most famous sinking occurred under the leadership of Milton Bradley who will forever be remembered for exclaiming to his foe, “You sank my battleship!”
That Yamato, or This one?
Indeed! Gorgeous ladies. 
Damn, The Massena is wonderfully ugly!
Not being a true Battleship Buff, I’ll just vote for our own Battleship Texas. She’s now located at the San Jacinto Battlefield, so the historically ignorant can see why Sam Houston beat Santa Anna!
:smack: I completely forgot about the battleship YaLego.
Not true. The Yamato fired her main batteries at attacking torpedo bombers. They were apparently not trying for direct hits, but to raise huge pillars of water in front of the planes for them to crash into. Didn’t work, and she was sunk in her one and only battle.
Who were the French expecting to fight in 1898,?
From the “Get A Bigger Hammer” school-of-thought: does this count?
Yamato’s 18-inch guns were equipped with “beehive” anti-aircraft shells; those were in fact what Yamato was trying to use.
Yamato had also participated in a battle in 1944 and was involved in a fairly serious battle a few weeks before being destroyed.
Is that some sort of shrapnel ?