[Imp]

Often more than one type of unit uses a weapon & they may have diffrent ammo loadouts due to their use or the time period & some ammo not being available.
The stats list the effects for all ammo types that weapon can fire, so the HEAT column is irrelivant if you dont have HEAT ammo.
Versus armour
HE uses the left PEN
AP uses the right PEN
SABOT uses APCR
HEAT uses HEAT

HE is as always mainly for use vs soft targets & the other types may well be fired at them to reserving the last 3 shots normaly for any armor.
This is all in the game guide