The Soldati. Level 28(with a level 31 remodel which only increases durability). 3 gun slots, with space 73/43/73. The best available guns are 5.5'' doubles unlocked when you get the ship, which require 69 space. 69>43...

Compared to other nations, similar DDs:

Tsukikei(IJN), lvl 24. At lvl 24, you get 5.5'' doubles with 5 gun slots
Z99(KM),  lvl 25 with 4 guns slots. By this level, you have access to 5.5-6'' guns
DDX, lvl 26(US) with 4 gun slots. Also at lvl 26, you can load it with 5.5'' doubles with 4 gun slots (some of which are available before lvl 26)
 L class(UK), lvl 24. 3 gun spaces, which are usually loaded with the trip 4''s
Mogador(MN), lvl 24. 4 gun spaces, and while the french don't have the best low level guns, each gun slot has the same space.
Leningrad(USSR), lvl 24. 3 gun slots, usually packed with the minizinis, until you unlock the 5.1'' doubles

75/43/75 on a lvl 28 ship is pathetic. It's bad enough ITY has bad low level guns, but when you finally give a decent ship and guns (5'' doubles, lvl 29, that require 69 space), give enough space to load it in all three slots!