Death by 1000 Cuts, IE Why shells won't shatter against armor when it's penetration value is lower than 18.5%

[JusticeForPetrolElectric]

Recently, I've been experimenting with different ship designs to try and find an alternative to mass battleship spam. Naturally, my first task was trying to figure out if any level of armor would make a ship immune to certain calibers. And so I found this post which mentioned that shots should always shatter vs armor when the pen value was less than 18.5% of the thickness: 

I started out with stubby 1.1 inch guns, and to my surprise even them could still casually damage manually designed battleships with ~11-20+ inches of modern armor everywhere in 1940s tech. In fact, I noticed that the DPS of guns peak at around 7.9inches, and that the 8.9 inch guns are uncommonly precise, much more than 9, 10, or 11 inch guns.

I was just wondering if that was intended behavior, that shells basically never shatter, and that a 8.9 inch gun is super precise, whereas a 9.9 inch gun is very imprecise...

Aside from the test you will find a print of my "death by 1000 cuts" heavy cruiser design with 6x 8.9inch guns in action against some 1925 tech stuff.

 

Edited September 30, 2023 by JusticeForPetrolElectric
Adding info