estimating the range can be permitted. There is but one way to overcome the difficulty, and that is by increasing the effective zone; and this can be done by using "combined sights," thus making two or more beaten zones which touch each other and overlap where the effective 75 per cent. of shots of both ends.
There are two ways of using combined sights:
(a) The "single gun" method.
(b) The "battery" method.
In (a), with an estimated range of 1,400 yards, the sights will be set for 1,300 and aim taken; then the sights will be again set for 1,500 yards, but without altering the original aim, and then "rapid" fire opened and the elevating wheel slowly turned to elevate the gun until the 1,500 yards sighting is aligned on the target. The result of this operation is to sweep the whole ground from 1,270 to 1,530 yards with effective fire; and if an error of 25 yards over or under the correct range has been made, the target is nevertheless brought within the effective zone by the combined elevations used. This is the best method for sections or single guns, and a section can vary this by one gun using 1,250 yards elevation and working up to 1,400, while the other gun begins at 1,350 and works up to 1,550. The choice of the amount over and under the estimated range must depend upon the ability of the person estimating the range and circumstances of the case, but less than 100 yards over or under should never be used.
