_Objects seem more distant_--

(_a_) When looking over a depression in the ground.

(_b_) When there is a poor light or a fog.

(_c_) When only a small part of the object can be seen.

(_d_) When looking from low ground upward toward higher ground.

=1397. Effect of heat and cold.= Heat causes shots to strike high, and cold causes them to strike low.

Therefore, if you shot on a warm day and made 5's, and recorded temperature and other conditions in your score-book, you would know on looking at your score sheets that you should raise your elevation, if you were firing on a cold day.

=1398. Effect of moisture.= Dampness causes shots to strike high and dryness causes them to strike low. Therefore, on damp days take lower elevations than on dry days.

=1399. Effect of light.= Light affects the aiming without the beginner knowing it. It does not, however, affect the travel of the bullet.

A dark target causes a tendency to aim farther below the bull's-eye than if the target were bright. Therefore, use higher elevations with dark targets. As it gets darker, higher elevations should be used.

If you _always aim carefully and correctly_ the light will have little effect on your aiming,--that is, if your eyesight is good.

If you are shooting in a dull light and a bright sun comes out, say on your right, there is a tendency to move the front sight to the opposite (left) side of the rear sight notch, since the near (right) edge is shaded and obscured somewhat. Therefore 1/4 to 1/2 windage into the sun (right in this case) should be taken to overcome this.

In using battle sight, hold higher for a bright light.

We also raise our sights if a strong sun comes out. Therefore, we have this rule: _Move your rear sight into the sun, just as you do for a wind,--and raise your elevation._

=1400. Mirage= gives a wavering appearance to the target. It is heated air that is moving. It is sometimes called "heat waves."

With the wind between 2 and 14 miles an hour on clear, hot days the waves can be seen moving across the target.

When there is no wind or a light six o'clock wind, the waves go straight up, or "boil." _Never fire when the mirage is boiling_,--wait for it to move from one side to the other and then take windage to correct for it.

=1401. Summary of temperature, light and moisture effects:=

_Raise elevation for_--

Dull target Shooting in the sun Hot gun Dirty gun Cold day Bright or shining sight Cloudy day 12 o'clock wind

_Lower elevation for_--

Bright target Target in sun Cold gun Clean gun Hot day Moist day Full sights 6 o'clock wind

=1402. Firing with bayonet fixed.= In firing with bayonet fixed usually a lower point on the target will be struck, corresponding to a reduction of about 50 yards in the range.

=1403. Care of rifle.= Since the accuracy of a soldier's rifle has a most important bearing on his shooting, and since the proper care of a rifle affects its accuracy, the care of the rifle is an important subject in which every soldier should be thoroughly instructed. The subject is fully covered in the preceding chapter. (Chapter XV, Part I).

COLLECTIVE INSTRUCTION

(Combat practice)

=1404. General scheme.= While individual instruction is most important, it is not everything. The maximum effect of fire in battle is obtained when a command, as a whole, is a pliable, manageable, effective instrument in the hands of a commander who can use it intelligently and efficiently. Therefore, the two objects to be obtained are:

1. To make the command a pliable, manageable, effective instrument in the hands of its commander.

2. To train and instruct the commander so that he will know how to use this instrument in an intelligent and efficient manner.

=1405. To make the fire unit a pliable, manageable, efficient instrument.= In order that a unit may be a pliable, manageable, efficient instrument in the hands of its commander, he must be able to control the unit absolutely,--that is to say, not only must the individuals composing the unit be so trained that they will respond at once, even in the din and confusion of battle, to the will of the commander, as expressed by his orders, but they must also be so instructed and disciplined that they can, as individual parts of the unit, perform their functions efficiently. This is accomplished by _fire discipline_.

=1406. Fire discipline.= By _fire discipline_ is meant a habit of obedience, a control of the rifle, and a display of intelligence, all the result of training, which will enable the soldier in action to make hits instead of misses. It embraces taking advantage of the ground; care in setting the sight and delivery of fire, including proper fire distribution; constant attention to the orders of the leaders and careful observation of the enemy; an increase of fire when the target is favorable, and a cessation of fire when the enemy disappears; economy of ammunition.

=1407. To train and instruct the commander to use the unit with intelligence and efficiency.= In order to handle the unit with intelligence and efficiency, utilizing to the greatest extent possible the power of all the rifles under his command, not only must the commander be able to control the unit, having it respond at once to his every command, but he must also know tactics, and be thoroughly familiar with the technical principles of infantry fire.

=1408. Combat exercises.= A combat exercise consists of the application of tactical principles to certain a.s.sumed battle situation, in the execution of which are employed the appropriate formations and movements of close and extended order drill, and in which, as a rule, ball cartridges are used in firing at the targets.

By means of combat exercises, the unit commanders are trained and instructed in applying tactical principles, in controlling and directing the fire of their units and the men are trained and instructed in fire discipline.

The tactical principles applicable to combat exercises are covered in the Infantry Drill Regulations, under the headings of "_Fire_" and "_Combat_."

=1409. Technical principles of firing.= The technical principles of firing are given in detail in the Small-Arms Firing Manual, a summary of which is given below under the headings of, _The Effect of Fire_, _The Influence of the Ground_, and _The Adjustment of Fire_.

The Effect of Fire

=1410. Ballistic qualities of the rifle.= The accuracy of a rifle, the flatness of its trajectory, and its disabling power,--that is, the power it has to disable the enemy,--are called its _ballistic qualities_.

The accuracy of the U. S. Springfield rifle, caliber .30, model of 1903, is very high,--probably superior to that of any other military rifle.

The flatness of trajectory is dependent upon the muzzle velocity, and, to some extent, upon the form of the bullet. Our bullet is pointed and the muzzle velocity is 2700 feet per second, which is a very high muzzle velocity.

Two rifles of different type may be equally accurate, but the accuracy of the one having the flatter trajectory will, naturally, be less affected by slight errors in sight setting.

Again, another advantage of the rifle with the flatter trajectory is that it holds more ground under its fire. For example, take our service rifle: At a range of 500 yards, the bullet, at the highest point in its trajectory or line of flight, is 2 feet above the line of sight. It is, therefore, apparent that if the bottom of an object 2 feet or greater, is aimed at, it would be struck if it were anywhere under 500 yards. Now, take a rifle with a very curved trajectory, say one whose bullet, at the highest point of the trajectory corresponding to a range of 500 yards, is 10 feet above the line of sight. There will be a large extent of ground between the target and the rifle that is not danger s.p.a.ce for a target 2 feet above the line of sight.

Hence, we see that the rifle with the flatter trajectory is better.

The continuous danger s.p.a.ce afforded by the flat trajectory of our service rifle enables us to adopt a universal sight for all ranges up to 500 yards,--that is, the battle sight, which is the rear sight ready for use when the sight leaf is laid down.

=1411. Cone of fire or cone of dispersion.= If a body of soldiers fire at the same target the bullets will not, of course, follow the same path, but will be scattered. This is due to differences in sights, parts of the rifle, ammunition, and to a greater extent, to the individual errors of the soldiers in aiming and firing.

The trajectories or paths of the bullets considered together form a horn-shaped figure or cone, called the _Cone of fire_ or cone of dispersion. (See Fig. 44.)

[Ill.u.s.tration: Fig. 44]

=1412. Shot group and center of impact.= If the _cone of fire_ be intercepted by a target (for example, A O, Fig. 44) at right angles to the axis of the cone, the shot holes will make a pattern or group called the _shot group_, the holes being the thickest approximately in the center of the group, called the _center of impact_. From this point in all directions the density of the grouping decreases progressively,--at first gradually, then more rapidly, out to the limits of the group.

Naturally, the size of the cone of fire and of the shot group vary with the skill of those firing, good shots making a small cone and small group, and poor shots a large cone and large group.