Direction for firing in fortress-siege artillery
Fire for adjustment (пристрелка). The direction emphasizes that the adjustment must be accurate, but also as fast as possible, in order to open the fire for effect before the enemy.
The adjustment is usually made with percussion shell without measuring the deflection of the projectiles.
It is aimed at finding the most probable elevation by :
a) capturing the target in the high bracket,
b) narrowing it by halving until the short bracket was obtained,
c) confirming the limits of the short bracket,
d) firing a group of shots carried out with the same data.
The short bracket is fixed at 4-8 deviations or, with bar sight graduated in meters, at 100 m. The high bracket is determined by increasing the short bracket by 2, 4, 8 times, according with the probable error in determining the distance. If already, the first shot is very short or very long or close to the target, then a high bracket wider or smaller than assumed can be taken.
In narrowing the range, if a sure shot is obtained on the target, at this elevation two observation are made :
if they are different (on straddle) shooting continues at the same elevation to execute the group;
if both the shots are seen on the same side, the distance is increased or decreased by a short bracket;
if the bracket is not obtained, the high bracket is further narrowed or a new bracket is sought.
If the observation is difficult, the adjustment is made by salvos with the high bracket.
The limits of the short brackets must be repeated to determine the elevation, starting at the final limit.
If the second observation of the limits of the short bracket is :
1) the same as the first ( or + +), the limit is regarded as confirmed;
2) opposite to the first, i.e. on straddle (+ or +), 2 or 4 observation more are made :
a) if the two following observations are on straddle ( + + or + +), the elevation is maintained and two more rounds are fired : if the group is satisfactory, the fire continued at the same elevation;
b) if the two following observations are equal to the last one ( + + + or + ), the verified limit is regarded as false, and the short bracket is sought again;
c) if the two following observations are opposite to the last one ( + or + + +), two more rounds are fired to obtain the group : if the ratio of short to high shots is satisfactory, the elevation is accepted, but if only one shot of the group is opposite to the others ( + or + + + + +), it is necessary to pass to the other limit, if it has not been verified, or move to the centre, it has been verified.
After the most probable elevation has been found, if any of the guns gives 3-4 equal observations, its elevation is changed by a short bracket and its adjustment is made separately according to the general rules.
If the fire is resumed after a few hours of interruption, the short bracket must be checked and if it turns out to be false, the elevation must be changed by a double width of the short bracket and the adjustment continues according with the general rules.
If the number of shrapnel with T&P fuze is great, the adjustment can be made with percussion shrapnel, firing by battery or platoon salvos to speed up the whole operation.
At first the adjustment is made with shell, exactly as above, but after having obtained the short bracket :
a) at distances up to 2500 m against targets in the open, the whole battery shifts to fire for effect, using time fuzes and firing in series (съ батарейни редове), aiming to the centre of the short bracket : according with the observations obtained from the first series, if necessary, the elevation and the bursting time of the fuze are corrected;
b) at ranges over 2500 m or against covered or partially covered targets and generally with mortars and short guns firing with time fuze, the limits of the short bracket are repeated, then the battery shifts to fire for effect, using time fuze and aiming to the centre of the bracket, if the two limits has been confirmed, or at one of the limits, if a shot on straddle has been obtained.
In the first case, the time of burst of the fuze is set immediately, in the second case it is set by identifying the most probable elevation. If the correspondence between the fuze and the elevation is not known, a platoon for the four-gun battery or two platoons for the six-gun battery switchs to time fire, while the percussion fire goes on at the same elevation of the time fire, until the correspondence is found, then the whole battery switchs to fire for effect with time fuze.
To set the fuze two rounds fired in succession must observed :
a) if they are very high or high, the fuze is lengthened by 0.8, 0.4 or 0.2 seconds, depending on the evaluation of the height of the bursts;
b) if two burst on graze are obtained, the fuze is shortened by 0.8 seconds and in any case not less than 4 probable deviations of the shrapnel in height (the probable deviation of the shrapnel in height is regarded as corresponding with the triple that of the shell height);
c) if one is high and one on graze, two more rounds are fired at the same elevation and with the same fuze, and if two low bursts are obtained, the fuze is shortened to obtain the required average height of burst.
Time fire is regarded as good when out of 6 shots no more than 1 bursts behind the target and if the average interval does not exceed 4 probable deviations of the shrapnel (about 100 m). The burst height is regarded satisfactory when of 6 shots 1 bursts very low or hits the ground.
Control rounds must be fired whenever there is any doubt as to the accuracy of the burst or their effect, firing two rounds or a full battery series (4-6 shots). They are fired at an elevation increased by 2 short brackets and the corresponding fuze lengthened for low bursts. Also in this case if a cannon gives different bursts from those of the others (all high or on graze), its elevation is corrected by a short bracket.
If there are not percussion shells or the target is placed where the observation is difficult (marshy land, with ravines, covered with tall and dense plants), the adjustment can be made with time shrapnel, firing by platoons with fuze set for low bursts. The short bracket is restricted up to 8 probable deviations, when their limits are confirmed, the fire is moved to the centre of bracket and the guns shifts to fire for effect by battery series.
The adjustment in direction is made starting with the deflection reported in the firing tables and taking into account the slope of the axis of the guns and the direction and power of the wind. With the start of the group, the direction of each cannon is checked individually. The adjustment is regarded as complete when out of 6 rounds, fired with the same lateral deviation, 2-4 rounds fall in the same part of the target.
The distribution of fire is carried out by gun or by platoon, according with the features and the size of the target, and after having repeated the short bracket, in order to obtain the distribution of the shells over the entire width of the target. Whit short target fire must be always concentrated.
The switch of fire must be always done to a closer target. If it is caused by the unexpected appearance of a danger a short distance from the battery, it takes place without a specific order from the superiors; otherwise, it can be carried out only according with an order.
If the battery is firing with shells or with shrapnel with percussion fuze, the fire is directed at a new target, giving the elevation corresponding to the distance and framing the target in 4-2 short brackets, then switching to time fire for effect at the small limit by rapid fire in succession.
If the battery is firing with time shrapnel, at first the guns shoot quickly at the old target, then they are loaded with shells or shrapnel with percussion fuzes and finally they switches the fire as above.
If the battery is firing with time shrapnel and the new target is near the old one, the elevation is reduced for percussion or low bursts fire to obtain indications about the distance to the new target, then the battery switches to fire for effect.
The direction gives also detailed information about the adjustment and fire with percussion shell measuring the deflection of the projectiles, and with time shrapnel measuring the interval and the height of burst.