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 space from the top of such obstacle to where the bullet strikes the ground (space B E, [Fig. 46]) will be protected from fire. Such space is called, "defiladed space." 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.
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 assume the kneeling or prone position, depending on how far away from D he was.
By cover is meant effective defilade from the enemy's fire.