I really struggle with this and armour thickness/penetration especially. I find it's just too much to take in (or can be bothered to learn which is more like it).

I just watched this video from Flambass but in the end my eyes just glazed over but he did leave a link to an article created by Little White Mouse which explains it in more simple terms.

Video...



And the all important link IFHE YES/NO

From LWM thread I kept this:

gun caliber in the 150/155 range=ifhe
other calibers=no ifhe

flambass gets it much more complicated, too much for my taste.