From this it follows that the good qualities of the machine gun can be utilized to the fullest advantage only when the appropriate elevation is used. When this is not accurately known, the fire effect of the machine gun drops down to zero more quickly than that of a skirmish line. Where local conditions are at all favorable, the determination of the appropriate elevation is facilitated by observing the strike of the projectiles in "volley fire."
According to British firing tests, at ranges from 500-1000 yards an
error of estimation of 100 yards, reduces the effect of the fire 50 per cent.
According to firing tests 75% of all shots fired by a machine gun and
body of infantry are distributed as follows:
======+==================+==================+====================
| Machine gun. | Detachment of |Errors of estimation
| | infantry. | permissible for the
At |Depth of 75% strip|Depth of 75% strip| machine gun.
m.
| m. | m. | m.
+++
450 | 112 | 192 | 54 = 12 %
900 | 63 | 108 | 31 = 3.5%
1350 | 54 | 90 | 27 = 2 %
1800 | 67 | 140 | 31 = 1.8%
+++
It is clearly apparent that the permissible error of the range finder is smaller than the depth of the vertical dispersion strip covered by 75% of the bullets.
The difficulty of hitting a target lodged in some feature of the terrain requires that the machine gun be used first of all against large targets that are visible for a short time only. When the appropriate elevation is used, a decisive effect may be confidently counted on within a short space of time; when an inappropriate elevation is used and the fire is not properly observed, only accidental hits can, as a rule, be expected, even when the fire is directed on tall, dense tragets. When the fire is directed on skirmishers lying down, the effect produced is not commensurate with the amount of ammunition expended, and a slight error in the elevation used may nullify the effect
