Another case of serious under-dotation - the South African Ratel 20 - Unit 27 - has a 10+10 round loadout in the game, while in reality it carries 1,200 20mm rounds (...and 6,000 7.62mm MG rounds...)- see
http://www.geocities.com/sa_bushwar2/ratel or 'Tanks of the World'.
If playing with such vehicles versus an opponent who has (correctly loaded) BMPs, for example, you'll run out of ammo pretty soon, and reloading takes time, provided you have bought ammo carriers...