Direct hits are necessary when it is used against guns, limbers, earthworks, obstacles, etc., and its effects are then due to percussion, penetration, and the explosive force of the bursting-charge. When used against men or horses, it is burst on first graze close in front of the target, and its effects are then produced by its splinters. The smoke made by the large bursting-charge of the percussion-shell aids the observation of fire.
The effect of projectiles with percussion-fuzes is dependent on the nature of the ground in front of the target; soft marshy ground, hollows, and cuts diminish its effect, while hard smooth ground increases it.
Percussion-shell gives the best results when the fire is concentrated. It can sometimes be advantageously distributed, provided that several guns keep a part of the target under superior fire.
Shrapnel with Time-fuze is used against all living targets, provided they be not close behind cover, troops behind slight cover, such as shelter-trenches, banks, etc., gun-pits and epaulments, balloons, batteries limbered up or in action, ammunition and other trains, unless firing particularly against the material. With the fuze set at zero it can be used for close defence in default of canister.
The effect of shrapnel is due to the penetration of its bullets and splinters; this penetration is small, and it is therefore employed against men and horses only. It has a combination fuze and can be made to burst either in the air or on the first graze, and can therefore be made independent of the nature of the ground in front of the target. Made to burst high by means of its time-fuze, it can be used against living targets behind cover, against which percussion-shell could have but little effect.
Burst the projectiles 50 yards short and about 6 yards (at medium ranges) above, the object aimed at. A rough rule for height of burst is height of burst in feet=the number of hundred yards in range. In firing at troops behind cover, such as banks, rising ground, or earthworks, burst the projectiles about 25 yards, or less, in front of, and from 7 to 10 feet above, the cover.
Shrapnel with Percussion-fuze is generally used against moving targets, for rapid firing, and for firing over friendly troops; against enemy's troops in a village or woods; metal shields; and in cavalry combats as soon as the ground which was masked by one's own troops becomes cleared.
Shrapnel gives the best results when the fire is distributed, a part of the target being apportioned to each gun. When the time-fuze is used, it will often be advisable to vary the elevation and length of fuze in each battery so as to cover about 200 yards in depth, and thus bring the enemy's supports and reserves, as well as his front line, under fire.
Canister is used against living targets at close ranges. Its effect is largely diminished when the ground in front of the guns is rough or soft, and particularly when covered with brush or standing crops. It would be used against cavalry at 500 yards, and against infantry at 300 yards.
Order of Fire.—The order of fire is habitually by piece in each battery, and usually commences on the leeward flank. It is the most effective, as the errors in the service of any one gun can generally be observed, and therefore corrected.