b. Exercise No. 5. Purpose: To teach use of sights and fingers for lateral measurement. Method: (1) A number of short vertical lines 1 foot apart are plainly marked on a wall or other vertical surface. At a distance of 20 feet from the wall a testing line is drawn or marked out by stakes. (2) The instructor explains that the vertical lines are one sight apart when measured from the testing line, so that the correct distance from the rifle sight leaf to the eye can be determined by pointing the rifle at the vertical lines and moving the eye along the stock until the raised sight leaf exactly covers the space between one of the vertical lines and the next line to the right or left. The instructor demonstrates with a rifle while explaining. (3) The men take positions on the testing line and each determines the proper distance of his eye from the sight as explained by the instructor. The position of the eye with reference to the stock is carefully noted or marked on the stock. (4) The instructor then explains and demonstrates the use of fingers in measuring sights. First he holds his hand, with palm to rear and fingers pointing upward, at such distance from his eye that each finger will measure one sight on the wall. Then, so that he can later redetermine this distance, he lowers his hand to his side without changing the angle of wrist or elbow and notes the exact point at which the hand strikes the body. Thereafter when measuring with the fingers he first places his hand at this predetermined point and raises his arm to the front without changing the angle of wrist or elbow. His hand will then be in the correct position for measuring sights by fingers. (5) The men determine the proper distance of fingers from the eye as explained by the instructor. (6) Practice in lateral measurement is given, using convenient objects within view and using both sights and fingers. c. Exercise No. 6. Purpose: Practice in target designation by pointing with the rifle. Method: (1) The squad, with the exception of the squad leader, is formed faced to the rear. The instructor then points out the target to the squad leader, who takes the kneeling or prone position, estimates the range, adjusts his sight, aligns his sights on the target, and then calls Ready. (2) The members of the squad then move in turn to a position directly behind the squad leader and look through the sights as illustrated in Plate 5, until they have located the target. The range is given verbally by the squad leader to each individual. If the target has width, the squad leader, after giving range, announces so many sights right or left. (3) As soon as each man has located the target, he moves to the right or left of the squad leader, sets his sight, places his rifle on the bayonet rest or sandbag and aligns his sights on the target. (4) The instructor, assisted by the squad leader, verifies the sight setting and the alignment of the sights of each rifle. d. Exercise No. 7. Purpose: Practice in target designation by verbal description. Method: (1) The squad is deployed faced to the rear. The squad leader is at the firing point, where sandbags or bayonet rests have been provided for seven rifles. (2) At a prearranged signal the target is indicated by the display of a flag. When the squad leader states that he understands the position of the target, the flag is withdrawn. (3) The squad is then brought to the firing point, placed in the prone position and each man required to set his sight, using the sandbag or bayonet rest to sight his rifle on the target, according to the verbal description of the squad leader. The squad leader gives his target designation from the prone position. (4) The squad leader's designation is checked from the ground. The men are required to leave their rifles, properly pointed, on the rests until checked by the instructor or squad leader. 23. Scope and importance.-A good workman knows his tools and understands their use. The soldier has learned the use of his rifle and is now to learn more of the action and effect of bullets. It is the bullet that kills. The soldier must also know the different kinds of rifle fire and their use if the best results are to be obtained. 24. The trajectory.-a. Flatness.-The trajectory is the path followed by the bullet in its flight through the air. The bullet leaves the rifle at the tremendous speed of 2,700 feet per second, and because of this speed the trajectory at ordinary ranges is very nearly straight or flat. Diagram of Trajectory Upper Line Shows Path of Bullet for Range of 1000 Yards Plate 11 shows the trajectory for a range of 1,000 yards. If the rifle is fired from the level of the ground on a flat plain, the bullet will rise to a height of only 15 feet above the ground during a flight of 1,000 yards. Since the vertical and horizontal distances are drawn to the same scale, Plate 11 gives a correct picture of the trajectory and shows how slightly it curves toward the ground. Plate 12 shows trajectories for several ranges. For convenience, the vertical scale is made 20 times the horizontal scale. This difference in scale means that vertical distances and the curvature are exaggerated 20 times in the drawing. The figures showing heights of trajectory are correct, but it must be remembered that the path of the bullet is not curved, as shown in this plate, but almost straight, as shown in Plate 11. The great advantage of a flat trajectory is that the bullet sweeps close to the ground and covers several hundred yards effectively with one sight setting. b. Angle of fall.—The angle at the target between the trajectory and a straight line to the gun is called the angle of fall. Due to the flatness of the trajectory, this angle will be very small at ordinary ranges. Angles of fall are shown in Plate 12. When the gun and target are on the same level and the slope of the ground at the target is the same as the angle of fall, the bullet will sweep along the ground for a long distance. A greater slope of the ground will mean that it is not covered at all. c. Danger space. Since the trajectory for a range of 700 yards does not rise above the height of a man standing (68 inches) it follows that, on level ground, all the space between the gun and target is dangerous, so that we say that the danger space for ranges up to 700 yards is continuous. For ranges of 800 yards and more the bullet does rise above the height of a man, so that only parts of the space between the gun and target are dangerous. The danger space then consists of two parts: First, the space from the rifle to the point at which the bullet rises to the height of a man; and, second, the space from the target to the point at which the bullet again falls to the height of a man. Danger spaces for several ranges are indicated at the bottom of Plate 12. If the enemy troops are kneeling or prone, the danger space will be reduced accordingly. 25. Dispersion.-a. Experience in rifle marksmanship shows that it is impossible for any man, and especially for any group of men, to fire a number of shots, so that all the bullets will follow exactly the same path. Due to differences in rifles, ammunition, aiming, and holding, the bullets are bound to scatter or disperse slightly. This effect is called dispersion. Dispersion may apply to a single rifle or to a group of rifles. Dispersion is greater in the case of the group because there are more variations to cause it. b. If tracer ammunition should be used in firing rapid-fire scores on the target range a man watching from a distance to one side of the range would see the tracers as a long, narrow cone of fire. The point of this cone would be at the firing point and its base at or beyond the targets. It is called the cone of dispersion. 26. Shot groups and beaten zone.-a. Shot groups.-When the cone of dispersion strikes a target, the bullet forming the cone will make a pattern upon it. This pattern is called a shot group. Groups made in firing on the rifle range are called vertical shot groups because they are made on a vertical target. Shot groups made on a horizontal target, or surface, are called horizontal shot groups. Due to the flatness of trajectory, horizontal shot groups have a length of from 100 to 400 yards, depending chiefly on the range. For ranges not exceeding 1,000 yards, the length of the horizontal shot group decreases when the range is increased. b. Grouping. The hits are not spread evenly over the entire shot group but are much closer together near the center of the group. This is true of both vertical and horizontal shot groups. c. Beaten zone.-The beaten zone is the ground struck by the bullets forming a cone of dispersion. When the ground is level the beaten zone is also a horizontal shot group. The slope of the ground has a great effect on the shape and size of the beaten zone. Rising ground shortens the beaten zone. Falling ground will escape fire unless its slope is less than the downward slope of the trajectory at the point considered. d. The danger zone. An enemy will be in danger if he is in the beaten zone or in the corresponding danger space. The addition of these two distances gives the danger zone as shown in Plate 13. 27. Kinds of fire.-a. Fire as regards direction is classified as follows: (1) Frontal: Fire delivered at right angles to the front of the enemy lines. (2) Oblique: Fire delivered at an oblique angle to the front of the enemy lines. (3) Enfilade: Fire delivered at the enemy from a position on the prolongation of his line. (4) Flanking: Fire used to sweep along the front of a defensive line and thus enfilade the attackers as they approach a position. (5) Reverse: Fire delivered so as to strike troops from their rear. b. Fire as regards trajectory is classified as follows: (1) Direct laying: Guns laid by directing line of sight on actual target. (2) Grazing: Fire which is approximately parallel and close to the ground. (3) Plunging: Fire which strikes the ground at a considerable angle. (4) Overhead: Fire delivered at objectives over the heads of friendly troops. c. Comparison.-Oblique fire is slightly more effective than frontal fire. Enfilade and flanking fire are more effective than oblique fire. Grazing fire is more effective than a plunging fire because the beaten zone is much longer. Only direct laying is used in musketry. Overhead fire with the rifle is safe when the ground affords protection to the friendly troops in front or when they are cient distance below the line of fire. Greater risks are taken in war than are advisable in training. a suffi d. Rule for firing at moving targets.-When firing at a man walking across your front At 100 yards, aim at the forward half of his body. e. Assault fire.--(1) Method.-While delivering assault fire, the firing line advances at a walk. Riflemen halt individually, aim and fire standing. They go forward a few steps, halt and fire again, keeping on a general line. They load while advancing. Bayonets are fixed before taking up the assault fire. The use of the sling by riflemen is optional. The automatic rifleman fires semiautomatic fire while steadily advancing. The piece is supported by the sling which passes over his left shoulder. He steadies his weapon by pressing the butt against his right side with the right elbow. Riflemen fire straight to the front. Automatic riflemen distribute their fire along the enemy lines within limits which will provide safety to the men on their right and left. (See Pl. 14.) (2) Use.-Assault fire can sometimes be used to advantage when within 150 yards of an enemy who is not returning the fire. Its moral effect may serve to keep the enemy down or drive him from the position. It has the disadvantage of making the attackers very conspicuous and vulnerable to the fire of any enemy troops within effective range. It has been used to advantage while advancing through woods in which the enemy positions were not accurately known. f. Use of the battle sight.-The battle sight corresponds to a range of about 550 yards. It is less accurate than the peep sight and is used only when time is lacking for setting the peep sight. By keeping the sight habitually set at 300 yards when not in use, the soldier has two sights ready for emergencies. 28. Firing at field targets.-a. Field targets are neutral-colored targets designed to look like soldiers when seen from a distance. The most common examples are the kneeling and prone olive-drab silhouettes issued by the Ordnance Department. When we say that success in musketry depends on individual marksmanship, we mean the ability to hit field targets as well as bull's-eyes. b. Ability to hit field targets requires practice, in addition to the regular known distance firing on A, B, and D targets for the reason that the field targets are much more difficult to see clearly and the eye requires development to meet the increased strain of sighting. c. The effect of the sight is to cut off a part of the light so that there is greater difficulty in seeing the target through the sight than with the naked eye. This is particularly true of the smaller peep sights. For field firing, peep sights smaller than No. 6 will not be used. No. 8 peeps are preferable when they can be obtained. d. Sometimes the soldier can see the target until he looks through the sights when it will disappear because of the effect described above. In this case he must remember the exact position of the target in relation to the more prominent objects around it and then aim at the point where he knows the target to be. Fleeting targets require the same method of sighting. 29. Concentrated fire. When the fire of a number of rifles is directed at a single point the result is concentrated fire. Machine guns and automatic rifle groups are suitable targets for concentrated fire. 30. Fire distribution.-a. Meaning.-Fire distribution is the application of fire to the whole extent of a line target. Proper fire distribution means that all parts of the target are kept under effective fire. b. Importance.-The enemy will usually be found in an irregular line of individuals or small groups. Some of these may be visible but others will not. Without a definite system of fire distribution the latter will escape the effect of our fire. Firing unmolested, these unseen men are the most dangerous of the enemy. A proper distribution of fire over the whole of the target will cause more casualties and greatly reduce the effect of the enemy fire. |