Hi Krakatoa,
as planned, the M-Class cruisers were to be equipped with the awful semi-automatic 37mm Flak C/30 twins.
So the drawing is true to the design in that respect.
An improved AAA-outfit for ships commissioned around 1944 would be logical, though. ("Barbara"-refits f.e.)
As a side note, the 40mm Bofors were never more than an interim solution until the 37mm Flak M43 could become available.
It seems like the KM never received more than about 100 captured guns to mount on its surface ships.
So fitting them with M42's or M43's might be a more realisitc approach.
To keep in line with the references, I'll leave the drawing as it is, though.
Assuming the 55mm cannon's problems were worked out and the design went into production, what are the chances this would have replaced the truly wretched 37mm?
Also, was the quad 30mm (which was to have replaced the quad 20mm on the Wirbelwind AA tank) ever considered for naval use? I know the twin 30mm certainly was but never actually entered service.
Just as an aside - I once read somewhere that the fact the He-162 Volksjager was fitted with two 20mm cannons and not the intended two 30mm cannons was not that the airframe couldn't handle the recoil but was instead the fact that the main factory producing the 30mm fell into Soviet hands...