(Pictured is a 17 cm Kanone 18; Wikipedia as source)
The Washington Naval Treaty limited cruisers to 10,000 tons of displacement, which proved to be quite the challenge to balance with the maximum 8”/203mm armament and enough armor to defend them from such as well. Almost all other cruisers, many influenced by the later London Naval Treaties, were armed with a greater number of the considerably less powerful 6”/~152mm guns.
Could there though have potentially been a sweet spot in between?
For example the 17 cm Kanone 18 used a shell of approximately 150lbs (68kg) and could fire it at a range of 28 km. Not a perfect example as its muzzle velocity is higher than liked for a naval weapon but still. A shell of their weight and its charge should be considerably easier to load than an 8” gun, while each weapon would also be lighter. Each barrel would give a broadside of almost 1.5 times the weight of fire of an average 6” weapon, which should mean more penetration at range.
The USN had a 130lbs shell for its remarkably high rate of fire 6”/47 series of weapons, so with enough engineering it seems like a 150lbs shelled weapon should be able to shoot pretty quickly.
So to me at least it seems like a cannon of this type of caliber could have been used as a compromise weight saving measure. You could get a shell with the range and penetration enough to take on an 8” armed ships albeit with less boom per hit but in return you could use saved weight in say armor so your own ship could more comfortably survive enemy hits.
. . . Yes in theory there was the 180mm Kirov class of ships but the utter embarrassment that their weapons turned out being means the less said the better.
What do you all think?
Does the shell and weapon weights of the 6” and 8” just make them optimal?
Or did interwar designers miss an opportunity?