Manual of Military Training Part 118

=1413. Beaten zone.= The intersection of the cone of dispersion with the surface of the ground is called the _beaten zone_.

If the surface of the ground is horizontal, the form of the _beaten zone_ is that of an ellipse with its longer axis in the direction of the line of fire, as shown in Fig. 45.

[Ill.u.s.tration: Fig. 45]

In view of the fact that at the long ranges the angle of fall of the bullets is much greater than at short ranges, it follows that at short ranges the elliptical figure (beaten zone) is much more elongated than at long ranges. In other words, the longer the range, the shorter is the depth of the beaten zone. This is shown in Fig. 45.

=1414. Uncertainty and ineffectiveness of long-range fire.= It follows from what has been said, that as the range increases the length of the beaten zone decreases,--that is, a less depth of ground is held under fire. That being the case, if an error is made in sight setting due, for example, to an incorrect estimate of the range, the proportionate loss of fire effect due to misplacement of the center of impact will be greater as the beaten zone is less,--that is, as the range is greater.

Furthermore, the difficulty of exact range determination increases with the distance, the two influences combining to make long-range fire uncertain and usually ineffective.

=1415. Zone of effective fire.= That portion of the ground which contains the best 75 per cent of the shots in the beaten zone, is called the _zone of effective fire_.

Effectiveness of Fire

=1416. Factors involved.= The effectiveness of fire depends upon these three factors:

(1) The percentage of hits made; (2) The number of targets. .h.i.t; (3) The time of execution.

That is to say, the effectiveness of fire is determined by the number of enemies disabled or targets. .h.i.t in a given time.

=1417. Percentage of hits.= By the percentage of hits is meant the proportion of all the bullets fired that hit the targets. For example, if 1000 bullets are fired and 750 hit the targets, then the percentage of hits is 75.

The percentage of hits depends upon the dispersion, and this is influenced by the precision of the arm, the range, the visibility of the target, the atmospheric conditions, the training and instruction of the troops, and upon their physical and moral state at the time. In addition, the percentage of hits also depends upon the character of the ground as favoring ricochet hits, upon the correct estimation of the range and the proper designation of the target.

=1418. Number of targets. .h.i.t.= The number of targets. .h.i.t,--that is, the distribution of fire,--may be affected by varying degrees of visibility, as men instinctively choose the more conspicuous marks as aiming points. Under any circ.u.mstances, a poor distribution of the hits made will be due to an absence of proper instructions from the leaders; or, in other words, to poor control, or else to a want of understanding or lack of obedience on the part of the men.

=1419. Time of execution.= The time of execution is important in that the gaining of fire superiority is dependent less upon obtaining high percentages of hits than upon making an absolutely large number of hits in a unit of time. There is necessarily a limit to the rapidity of fire which, if exceeded, will result in some loss of accuracy. With targets of a fair degree of visibility, the following may be taken as standard rates of fire for troops who have been given suitable training in target practice:

200 yards } 300 yards } 10 shots per minute.

400 yards }

500 yards } 600 yards } 7.5 shots per minute.

700 yards }

800 yards } 900 yards } 5 shots per minute.

1,000 yards }

Greater ranges, 3 shots per minute.

The rates given should not exclude higher rates of fire in the case of large and conspicuous targets. On the other hand, when objectives, or marks used as aiming points, are very indistinct, the requirement of correct aiming imposes rates of fire somewhat lower than the standard rates given even for well-instructed men.

With imperfectly trained men who have not fully acquired the habit of using aimed fire only, and who are lacking in the manual dexterity required for executing the standard rates of fire, the maximum rate can not well exceed six shots per minute without incurring the danger of lapsing into unaimed fire.

Fatigue and exhaustion, the results of marches or prolonged firing, have a detrimental influence and tend to lower the rates of effective fire.

Influence of Ground

=1420. Defilade.= If we will consider a bullet just grazing the top of an impenetrable obstacle (like "A," Fig. 46), the s.p.a.ce from the top of such obstacle to where the bullet strikes the ground (s.p.a.ce B E, Fig. 46) will be protected from fire. Such s.p.a.ce is called, "_defiladed s.p.a.ce_." Its extent will, of course, depend on the height of the obstacle, the curvature of the trajectory and the slope of the ground in rear of the obstacles.

[Ill.u.s.tration: Fig. 46]

Between B and D, a soldier standing would be completely protected; between D and E, he would be only partially protected. To obtain complete protection between D and E the soldier would have to a.s.sume the kneeling or p.r.o.ne position, depending on how far away from D he was.

By cover is meant effective defilade from the enemy's fire.

By concealment is meant screening from view but not necessarily protection from fire.

=1421. Rising and falling ground.= The influence of the ground upon the effect of fire is at once seen by studying Fig. 44.

If the ground rises, as shown by B O and A O, the depth of the beaten zone (and consequently the effect of fire) decreases. On the other hand, if the ground falls (up to a certain point), the depth of the beaten zone (and consequently the effect of fire) increases.

=1422. Depth of beaten zone affects only targets having depth.= It should be remembered that depth of beaten zone can affect only targets which have depth.

On a target in the form of a line,--a line of skirmishers, for example,--the depth of the beaten zone has no effect one way or the other. If such a target, however, is backed up by supports and reserves, the depth of the beaten zone may have a decided effect on them, depending upon their distance in rear of the line forming the target and the slope of the ground in rear of such target.

In this connection, attention is invited to Fig. 47, which shows how in the case of a fire delivered from a height at a target on a horizontal plane beneath, the beaten zone is shortened and consequently the fire effect decreased.

[Ill.u.s.tration: Fig. 47]

An example of increasing the depth of beaten zone is seen in Fig. 48, which shows a fire delivered from low ground at a target on the edge of a plateau or crest of a ridge from which the ground slopes to the rear.

[Ill.u.s.tration: Fig. 48]

=1423. Grazing fire.= Shots which pa.s.s over a crest with an angle of fall conforming, or nearly conforming, to the slope of the ground beyond the edge of the crest (as shown in Fig. 48), are called _grazing shots_ and fire so delivered is called _grazing fire_.

=1424. Diminution or increase in fire effect due to rising and falling ground.= In connection with the diminution or increase in fire effect due to rising and falling ground, attention is invited to the following:

1. If the ground slopes upward to the rear from a firing line, the supports may be placed closer without increasing the danger from fire aimed at the firing line.

2. When the ground slopes down and to the rear from the firing line forming the target, the supports must be posted at a greater distance in rear, unless the slope is so much greater than the angle of fall of the hostile bullets that a defiladed s.p.a.ce is created in which no bullets strike, in which case the supports may be brought up close to the crest.

3. On ground rising with respect to the line of sight, column targets (i. e., having depth) will suffer greater losses than lineal targets.

4. On ground falling with respect to the line of sight, the reverse slope of hills or the level grounds of plateaus, line targets will suffer the greater losses.

=1425. Ricochet shots.= When a bullet strikes any surface and is deflected it is called a _ricochet shot_.

Not only do bullets that ricochet usually tumble after striking, but they are also mutilated, so that wounds inflicted by ricochet hits are usually severe.

The most favorable ground for ricochets is a smooth, hard, horizontal surface, the aim being low, the chance of ricochets in sand is very slight.

=1426. Occupation of ground.= The question of the occupation of ground presents these two aspects:

1. What firing positions may be chosen which will tend to increase the losses of the enemy?

2. What positions may be chosen and formations adopted to minimize our own losses?