Where are you supposed to aim your guns on periscopes?
 

Are you supposed to try to get a direct hit on the periscope to get it hit by shrapnel? Or are you supposed to aim a bit lower to try and get a shot to connect with the tower that's underwater?

To my mind, if you can see a periscope from a gunners station, you're not using them right. Guns are for use at extreme range using radar guided shells to cause the u-boat to dive. This slows it down enough to keep it out of firing range of the convoy. In a sense, the guns allow for the time required to get destroyers (initially) then corvettes into DC range. Instead of trying to use guns at close range, use the feather to make a really good DC attack in?