Interesting, so you're telling me the 88s and 105s on the U-boats use the exact same sound file as all the US and IJN cannon? Gotta run some tests, I hear the clang from IJN cruisers and destroyers when close up in external view, but not from a distance. Wild guess for now;
Close sound: P09_$Gun_muzzle_flash.wav
Distant sound: Cannon.wav
To check that I'll change Cannon.wav to something weird like a banshee wail from Oblivion or something, then pop up to the surface in the middle of a task force so they can blast away at me. BANZAI!