The rule of the thumb is, always at 0 angle with barrels. Unless the normal angle is something else... aside the russian Novik's, there are really few ships with that sort of feature, this one migth be one of them.
Proplem is, that Shipbucket style doesen't really allow (in ways of looking nice) to drawn angled barrels, so thats why the rule has more aesthetical purpose...
How did the source drawing place the barrels? Care to post that one and I could try to figure out something...
I can post the original line drawings from LaCroix and Willis as well as about fifty different pictures, but finding them on the internet is slightly hard; nonetheless:
Chokai, sistership:
A bit distant, but here are the barrels at elevation on Takao:
Japanese cruiser Maya, also of same class, barrels at elevation:
The cover of the book I'm using as a reference:
And so on. I'll upload the plan drawings from said book if you insist, but the simple fact is that No.3 turret could not go to zero degrees train without the barrels at 5 degrees elevation. This was a design feature, and not problematic, because the turrets used on the class had fixed elevation loading at 5 degrees.