What is the different between Pzgr39(40) and HEAT？
 

I want to know the difference between them in reallife and SF.....
when you press key 3 will choose the HEAT(High expolsive anti tank)rounds,and the Pzgr39/40 round is key 1,is there any different between them?

it seems the two rounds are anti tank shells........

The Pzgr39/40 was a kinetic energy round with a HE filler - Uses speed and mass to punch through the armour then explode http://en.wikipedia.org/wiki/Panzergranate_39

H.E.A.T basically burns through the armour http://en.wikipedia.org/wiki/High_ex...i-tank_warhead