Shipbucket

Mate, the Vernon Baker is missing a lot of detail. Your fonts are all wrong and not in-line with SB standards. But, the enthusiasm is there...

my mod of I-400 into the I-460. hanger replaced with magazine for 1 x16in gun

forget the magazine. the hangar will be only large enough for the gun itself (if it even fits) the gun can only aim a few degrees up.
that said, you don't have to worry about the magazine because your sub might go to pieces altogether at the first shot: I have doubts about the superstructure supporting the weight and recoil blast.
(your main problem, where all the above come from, is that the gun is waaaay too big)

acelanceloet wrote:forget the magazine. the hangar will be only large enough for the gun itself (if it even fits) the gun can only aim a few degrees up.
that said, you don't have to worry about the magazine because your sub might go to pieces altogether at the first shot: I have doubts about the superstructure supporting the weight and recoil blast.
(your main problem, where all the above come from, is that the gun is waaaay too big)

That and it'll probably destroy the now-superfluous launch ramp. I attempted something similar (with a twin 14-inch turret) in a long-forgotten AU once, but I also enlarged the sub greatly to compensate.

this is a rough drawing of USS la crosse it will eventually have 32x 5in guns in dual and quad turrets

take a look and comment

What exactly is that submarine for, what do you need 32 5" guns for?

Well...
Regarding the AA cruiser, very doubtfully. I don't think that hull(which is very blocky, making high speeds impossible) can carry that amount of guns.
Also, quad turrets are infamous for being overly complex and prone to breakdown, often hampered by jaming and slow rate of fire(the general rule is: the more guns you fit in a turret, the slower will each individual gun fire). They will also be very heavy, making training and elevation too slow to serve effectively.
There are reasons why the most succesfull DP mounts of that era was in twin mounts: it was simply the most balanced alternative.
I would also suggest you read this thread, especially the comments from Klags.
And lastly, and this goes for all ships you've made so far: Just becouse it looks like it can fit(on the surface), doesn't mean it will. You will have to take bellow-deck structure into account as well. Please, visit this thread for more notes on this.

A number of the 5" turrets literally do not have the space to train onto the beams. Minor side detail, I guess...

it would be more like a AA battleship than a cruiser, i was trying to take double the with of atlanta class and made it 750 ft long or so