Oh dear, HESH is High Explosive Squash Head! But HE does not squash against the armour and can be fired from a smooth bore.
I don't know where you get the idea of ''reflected energy''; reflected off what? Dissipated or absorbed by the armour would be more to the point.
I think you need to stop listening to ''people on the internet'', and do some research into the basics, read a book or two; anything by Ian Hogg, for example, would be good. Then apply some logic.
Also think about this; you got an answer from Ssnake and he makes a living from selling this software to national armies. Surely the model he uses would be valid enough for their training.