The following are the important causes which vary the direction and in tensity of the forces acting on the bullet, and which may be greatly obviated by carefulness and an understanding of the subject: r. A frequent cause of inaccuracy of fire is a false or defective barrel, short swells and long depressions being often found on its interior. These swells or ridges, by increasing the friction, may so effect the recoil as to have an injurious effect on the fire, or so affect the exterior form of the bullet as to produce an irregularity in its motion. The depressions or swells change the interior lines of the piece and give the bullet a false direction.
2. Another cause of inaccuracy of fire is the vibration of the barrel when firing, caused by the want of a homogeneous distribution of metal about its axis, and often to binding bands. These vibrations tend to alter the direction of the bullet as it leaves the muzzle.
3. Recoil causes the man to turn to the side from which he fires, and pro duces deviation in that direction. It is supported by pressing the butt firmly against the shoulder with the right hand, the left hand supporting the weight of the rifle, and varies with the position of the rifle relative to the horizontal, being a maximum when the shot is fired vertically upward. The shock of the recoil against the shoulder is diminished by the bend in the stock, serving to decompose the force into two components, one acting through the stock against the shoulder the other in the direction of the axis of the barrel, tend- ' ing to raise it. Whatever lessens the recoil theoretically increases the range.
4. When the bullet reaches the muzzle of the rifle, it will revolve about its axis nearly 800 times in a second, and a point on its exterior side surface will have an axial velocity of about ninety feet per second. This in connection with the resistance of the air produces a lateral drifting of the bullet in the ' direction in which the grooves have a turn. This is known as drift, and is greater in the descending than in the ascending branch of the trajectory. It increases as the diameter of the bullet, the angle of fire, the velocity of rotation and the range increase, and as the velocity of translation decreases. The drift in the Springfield rifle (caliber 45, seventy grains powder) at Soo yards is two feet.
3. The pull of the trigger should not be too great, a three-pound pull be- ' ing the minimum. It should be pressed by a steadily increasing pressure of the finger in the direction of the axis of the barrel, without communicating motion to the rifle, the breath being held until the hammer falls. If the
trigger is too hard and is pulled convulsively, the muzzle will be turned to the right. There should be a quick and decided connection between the mind and finger. Few men can pull off the trigger of our average service rifle with the first joint of a single finger. I have frequently supported the whole weight of the rifle, at full cock, on the trigger, without pulling it off. and I consider this a very serious defect. Every man should invariably fire his own and the same gun, in order to become acquainted with its defects of construction, and learn how to make allowances for consequent deviations from the theoretical trajectory.
6. The principal cause of the inaccuracy of most rifles is that they are sighted too coarsely. Without apparent movement, the rifle may be sighted on any object within a horizontal radius of many feet. I think it best to re place the ordinary bead sight by the Beach Combination Sight, which is such that it forms either an open bead or a globe sight with cover, according as the leaf is turned up or down, thus adapting it either to hunting or target use (and if I mistake not our frontier field service is more on the order of hunting than range practice). The globe of this sight is so constructed as to permit the use of all descriptions of sights, detachable pieces of the vari ous forms in use being slipped into a slot in the globe and held by a screw.
The Lyman sight is a most excellent one when the target is a moving object. When aiming, it has the appearance of a ring or hoop which shows the front sight and the object aimed at, without intercepting any part of the view. Its rim may be instantly changed to give it a large aperture with a narrow rim, or a small aperture with a wider rim. For all quick shooting the large aperture should be used. It possesses the following advantages: it allows an instantaneous aim to be taken—the object being sighted as quickly as if only the front sight were used; it readily permits one to shoot moving objects, running or flying, with both the eyes in use; it is also very accurate, eimple and strong. Any kind of front sight may be used with it, and it may be put on any rifle in the same way that a peep sight is attached and adjusted ' 1 or shooting any distance up to L000 yards.