the 'initspeed' command found in the CfgWeapon section simulates bullet drop nicely.
It determines the muzzle velocity of the weapon and is in metres per second units (e.g. 1000ms is 'initspeed=1000;').
You don't often see bullet drop because the speed is usually set very high and/or the view range doesn't allow it.
But try setting an initspeed of 300ms on a machine gun with tracers, fire at a point well in the distance, and you'll see the bullet stream fall well below where you are actually aiming.