Chapter IX: Part II: Section I

POINTING GUNS AND HOWITZERS.

1. What is meant by the term _pointing_ a piece?

To point a piece, is to give it such a direction and elevation, or depression, that the shot may strike the object; and the rule (except in case of mortars) is: First give the _direction_ and then the _elevation_, or depression.

2. When a shot is fired from a piece, by how many forces is it acted on?

By three.—1st. The impulsive force of the powder, which urges it forward.

2d. The resistance of the air, which tends to stop it.

3d. The force of gravity which causes it to descend.

3. Why is it necessary to give a certain degree of elevation to a piece?

Because a shot describes under the action of the above forces a curve called a trajectory, which is situated below the prolongation of the axis of the piece, the extent of its departure from _this line_ increasing with the time of flight. Therefore, the more distant the object, the greater must be the elevation to enable the shot to reach it.

4. How is the direction given to a gun or howitzer?

By directing the line of metal upon the object.

[Sidenote: 52]]

5. How is the elevation or depression given?

The elevation or depression, which depends upon the charge, the distance, and the position of the object above or below the battery, must be ascertained from tables or by experiment, and the proper degree given by means of instruments.

6. When will the object be struck by merely directing the line of metal upon it?

But in one case,—when it is at point-blank distance.

7. How must the line of metal be directed for all ranges less than the point-blank range, in order to strike it?

So as to pass below the object.

8. Give a simple rule for firing at objects within point-blank.

Add to the point-blank range the difference between it and the required range, set the scale to the elevation corresponding to this sum, as shown by tables of firing. Then aim the gun directly at the object; now apply the scale, and observe where the visual ray of the scale strikes the ground, and having noted this point, aim the gun directly at it.

9. How must the line of metal be directed for ranges greater than the point-blank range, in order to strike it?

Above it.

10. When the line of metal passes over the object, what instruments must be employed for giving the proper elevation?

The gunner’s quadrant, or the breech-sight.

[Sidenote: 53]]

11. How is the quadrant used?

After the direction has been given, the quadrant is applied, either by its longer branch to the face of the piece, or this branch is run into the bore parallel with the axis, or it may be applied to the upper surface of the lock-piece, making the allowance due to its inclination with the axis of the piece, which ought to be previously determined, and the elevating screw turned, or the quoin adjusted, until the required degree is indicated.

12. How is the breech-sight used?

It is first set to the elevation corresponding to the distance; it is then applied to the highest point of metal on the base-ring, and by the elevating screw, or quoin, the notch of the breech-sight, the highest point on the swell of the muzzle, and the object, are brought in the same line.

13. What is a line thus determined called?

An artificial line of sight.

14. In the absence of instruments, how may the elevation be given?

By placing one or more fingers of the left hand upon the base-ring, perpendicular to the axis, and using them as a breech-sight.

=NOTE.=—In practice, it is well to fire two or
three shot to determine the _range_ experimentally,
as _it_ is affected by divers causes.

15. Should the line of metal be always directed in the vertical plane passing through the object?

No; as in practice there are circumstances (as, for instance, a strong wind blowing across the field of fire) which will cause a ball to deviate from this plane, it follows that to strike the object, in such a case, the line of metal must be directed to its right or left; the gunner judging of the distance by observing the striking of the shot.

[Sidenote: 54]]

16. Is the line of metal a permanent line under all circumstances?

No; in batteries for garrison and sea-coast defense, where the platforms are fixed, the line of metal may be considered as nearly permanent; but with siege guns, which are mounted on traveling carriages, the wheels of which are liable to vary in position from unevenness of ground, or unequal settling in newly constructed platforms, this line is constantly changing. It approximates the higher wheel in proportion to the difference of level between the wheels; and hence, to secure the greatest accuracy of fire, it must be frequently verified; the old marks, if not found correct, should be erased and new ones substituted.

17. When the notches or sights, which are sometimes made upon the base-ring and swell of the muzzle in field guns, for aiming the piece are used, how is the error of direction remedied when the wheels are not on the same level?

The piece must be aimed more or less to that side which corresponds to the higher wheel, according to the inclination.

18. When the elevation or depression has once been ascertained for any given distance, how may the firing at that distance be facilitated?

By noting some point on the elevating screw or quoin; adjusting some fixed measurement from a point on the stock to another point on the under side of the breech; or by a chalk mark drawn across the face of a trunnion and its corresponding cheek.

[Sidenote: 55]]

19. When firing either within or beyond point-blank range, may remarkable points on the ground be taken advantage of, in order to furnish an object to aim at?

Yes; some fixed object may often present itself which will serve as a point upon which to direct the line of metal. No means should be neglected that may tend to secure accuracy of aim; for the shot that is thrown away by carelessness in pointing, had better not be thrown at all.

20. How may precision of fire be secured at night?

When a fixed object is to be fired at by night, the piece should be directed during the day, and two narrow and well-dressed strips of wood laid on the inside of the wheels, and two others outside of the trail of a siege carriage, and nailed or screwed to the platform. In case of a barbette carriage, the traverse-wheels should be chocked in the proper position. To preserve the elevation, measure the height of the elevating screw above its box, or take the measure between a point on the gun, and another on the stock; cut a stick to this length and adjust the gun on it at each fire.

21. Should night-firing with _guns_ be limited?

Yes; it should be limited to a small number of rounds, as it consumes ammunition to little advantage.

[Sidenote: 56]]