Shooting isn't simply a matter of pointing your weapon at the target and letting fly. Factors other than your Ballistic Skill affect the chance of hitting, such as range and cover as already discussed. There are other factors too, some of which make it easier to hit, and others that make it harder.

Factors that make it easier are added to your die roll. Factors that make it harder are subtracted from your dice roll.

+1 Shooting at a Large Target

A large target is anything which in real life would stand over approximately 10 feet tall or which is especially bulky. Ogres and Trolls are large targets for example, while Men, Orcs, Elves and the vast majority of troops are not. Cavalry models are not considered to be large targets if they are riding horses, wolves, boars or comparable beasts. Large monsters, chariots and most war machines are large targets.

-1 Shooting While Moving

If the shooter moved during the movement phase then his chance of hitting is reduced. Even a simple turn or change of formation is enough to reduce his concentration and so counts as movement for this purpose.

-1 Shooting at a Charging Enemy

If you are charged and elect to stand and shoot at your attacker then your chance of hitting is reduced. While the enemy thunder towards you your aim will be distracted and your shot hurried as you abandon your weapon to take up a sword.

-1 Shooting at Long Range

If your target lies at over half your maximum range you are less likely to hit. Sometimes you will find some of the shooters are within short range and some are at long range. If this is the case you must roll two batches of dice, one for each range band.

-1 Shooting at a Single Character Model or Skirmishers

If your target is a single man-sized character model, whether on foot or cavalry, then this penalty applies. The penalty also applies when shooting at enemy in a skirmish formation, or at any single man-sized model on its own. See the section on Heroes and Wizards for a complete explanation of rules for shooting at character models, and see the section on Skirmishers for rules regarding skirmishing troops.

-1 Target is Behind Soft Cover

If your target is behind soft cover then your chance of hitting is reduced.

-2 Target is Behind Hard Cover

If your target is behind hard cover your chance of hitting is drastically reduced.

All shooting to hit modifiers are cumulative. So, for example, if you are shooting at long range at a target behind soft cover your chance of hitting is reduced by -2. This means that with a BS of 5 you would need to roll a 4 to hit instead of the 2 normally required.

For example: 10 Goblin archers open fire at a unit of Elves. The Goblins have a BS of 3 and their targets are 10" away. To make matters worse, the Elves are standing behind a hedge - soft cover! The bold Gobbo ladz are armed with short bows which means their targets are at long range (short range being 8" or less for these weapons). Because their BS is 3 the Gobbos need a 4 to hit but since their targets are in cover and at long range this means that they suffer a penalty of -2. So each archer needs to roll a 6 to hit as 6-2 = the 4 required. The player rolls 10 dice and manages to get two 6's two bits!