Rules for adjustment and firing

 

 

 

 

The first Bulgarian instructions for the artillery fire were the Rules for artillery adjustment and fire, the so-called “Red booklet”, introduced in 1889 by the Artillery Inspector lt.col. Petar Tantilov, adapting the Russian Rules for firing for field batteries (Правила стрельбы для полевой батареи), proposed two years before by the Russian general major Vladimir Nikolaevich Shklarevich. This first Bulgarian handbook followed strictly the doctrines of the Russian Artillery School and the theories exposed in the French Revue d’Artillerie by major Alexandre Percin, who, as teacher of artillery at the École spéciale militaire de Saint Cyr, at that time was beginning to reform the tactics of the artillery, especially about firing with time fuze.

The “Red booklet” was completed with the Hand-tables for the firing data (Наръчни таблици за даните на стрелба), elaborated on the basis of the data furnished by the factory. These firing tables included the angle of elevation and the lateral deviation for every range from 100 m to 100 m, as well as the information required to calculate the trajectory and the mean dispersion of the shots. Being obtained in ideal conditions with a new guns, however, the theoretical data was often very different by the real one, especially the dispersion might be even two-fold greater in action with guns in different level of wear.

All the rules and the directives were addressed to the battery, which was regarded as the basic unit of artillery. Being composed by 4 two-guns sections, it could be employed both as a whole, and subdivided into sub-units, acting by half-batteries, sections and, exceptionally, also single guns. No direction was anticipated for the employ of the greater units, like the artillery division or the regiment. The first instructions for the employ of a group of batteries were published only two years later, in 1891.

 

The Rules included the following chapters :

a)     Features of the projectiles.

b)     General rules for firing.

c)     Preparatory fire.

d)     Adjustment and fire at close range.

e)     Adjustment when it is difficult to distinguish the rounds over the target from the short rounds.

f)       Firing at moving targets.

g)     Scale fire.

h)     Firing at targets unseen by the aimer.

i)        Shelling targets sheltered in dugouts and earthworks.

j)       Accountancy.

k)      Tasks of the protective and observation lines.

 

The projectiles. The first chapter described in detail the main features and the effects of the various kinds of projectiles, employed at that time by the Bulgarian artillery. Great importance was deserved to the impact of an inaccurate determination of the height of sight on the accuracy of the fire.

The common shell (граната), acting both by the burst of the charge and by the striking energy of its splinters, could be employed against all the targets that should appear in a field battle, both animate and inanimate. It was equipped with percussion fuze, working on impact. Its effect depended on the character of the ground and on the distance of the target. Unlike the principal European regulations, that recommended to employ it only at a distance not greater than 2500 m, the “Red booklet” regarded it effective also at great ranges (even more than 3000 m), if the ground was hard enough.

The shrapnel (шрапнел) was equipped with a fuze that enabled to set with precision the rate of burning. It burst into the air, before having hit the ground, and spread the bullets on the target. The effect of the bullets on animate targets depended upon their striking energy and their sectional density, those of smaller diameter having the greater penetration. The main problem was to know the point of burst that was determined by the interval of burst (the horizontal distance between the point of burst and the target), and the height of burst (the vertical distance of the point of burst above the horizon). The closer the point of burst was to the target, the greater was the velocity and, consequently, the effect of the bullets. The normal interval was set at 80 m at close ranges (up to 1500 m), at 60 m at medium ranges (up to 2500 m), and at 40 m at great ranges, the normal interval being regarded as the most satisfactory. The “Red booklet” emphasized the importance of a correct determination of the point of burst, to avoid that it was too before or behind the target. An error of 1 graduation (approximately 20 m) in the long side caused very little losses; an error of 2 divisions (40 m) in the short side halved the losses, and a mistake of 3-4 division (60-80 m) in the short side made the fire almost ineffective. The extent of the area effectively beaten by the shrapnel bullets was indeed greatly underestimated, since the booklet affirmed that the bullets were effective only in an area 15 m wide and that half of the losses gathered in an area 5 m wide. In fact, according with the estimate of the time, the whole area of diffusion of the bullets was 60 m wide, and 82% of the hits gathered in an area 30 m wide.

The case shot (картеч) was a cylindrical zinc case filled with round balls and was employed only against animate targets at close ranges (400 – 500 m). It shattered already in the barrel and its splinters and the balls spread out in a conical form, causing a wide swath of destruction.

The sharoha (шароха) was a cylindrical cast iron shell, whose head was a ball that continued to roll after the burst of the proper shell, hitting the troops placed behind the front line. It was regarded as ineffective already during the Russo-Turkish (1877-78) and in Russia its production had been stopped in 1876. It was assigned in little number only to the old Russian 9 pdr and 4 pdr field guns.

 

Generalities. Besides the general rules for firing, the description of the individual duties in the service of the piece and the direction about the correct manner to bring the gun into position, the “Red booklet” dealt at length with the care of ammunition and artillery materiel. It was a matter of the highest importance their correct storage and maintenance, since their working order greatly affected the accuracy of fire. In order that all the parts worked easily and without unnecessary wear, the materiel should be kept properly lubricated, assuring the constant maintenance of a thin film of the proper lubricant between all working and bearing surfaces and the surfaces on which they work or bear. Special attention should be paid to the breech-block, whose mechanism should always work perfectly to avoid severe accidents. 

Preliminary fire (подготвителна стрелба) was used to provide the recruits with a little knowledge of the firing theory, showing them how the fall of the projectiles depended upon the height of the sight and other adverse conditions, like the battering charge, a wrong measurement, inadequate maintenance of the materiel and so on. 

 

Fire for adjustment (пристрелка). The purpose of the adjustment in elevation (определение на мерника) was to find the distance (height of sight) up to the target as quickly and accurately as possible, according with the real situation and the features of the projectile employed. The most probable distance was at the middle of the bracket obtained firing a shot in front and another behind the target (нулева вилка = straddle). Accurate though the adjustment might be, a margin of error would be always, owing to the dispersion of the shots and other accidental factors. The probable error was reduced according with the law of probability, by lowering down the bracket and by the repetition of the same observation.

The ranging fire could be effected in three different ways :

    directly with shell : it was employed against targets standing immobile into the open, usually starting with a bracket not lower than 8 and not higher than 16 graduations. If the first round was short, the range was increased; if over, it was decreased; and rounds were fired successively increased or decreased in range until the target was bracketed. Then the size of the bracket was successively reduced by halving the last bracket obtained to 2 graduations for a range up to 3000 m and to 4 graduations for greater ranges.

The final limit of the bracket was repeated with another shot, to find the most probable height of the sight, and :

a)     if the straddle was obtained, the other limit of the bracket was not repeated and the fire continued without changing the height of sight : low bracket at 50-52 graduations, repeating the short limit (50) and obtaining − +,  the most probable height of the sight was at 52, or repeating the large limit (52) and obtaining − +, the most probable height the of sight was at 52;

b)     if it was like the first observation, the other limit of the low bracket was repeated and if this time the straddle was obtained, the fire continued without changing the height of sight : low bracket at 50-52 graduations, repeating the short limit (50) and obtaining − −, the large limit (52) was repeated and obtaining + −, the most probable height of the sight was at 52 (beginning with the large limit the process was the same);

c)     if the straddle was not obtained even at the other limit, the fire was directed at the middle of the low bracket : low bracket at 50-52 graduations, repeating the short limit (50) and obtaining − −, and the large limit (52) and obtaining + +, the most probable height of the sight was at 51.

The most probable height of the sight should be verified firing a group of four shots. When some of the rounds were short and some over the targets owing to the dispersion of the shells, and not by an error in aiming the gun or by accident, the adjustment was regarded as finished and the guns shifted to fire for effect. The “Red booklet” listed five different cases that might occur during the ranging fire, showing what the battery commander had to do in each of them.

    with shell and shifting to shrapnel : at first the adjustment was made with shell, exactly as above, but after having fired the group of 4 shots, one or two sections shifted to shrapnel fire. The height of the sight for them was 1 or 2 graduations lower than the height that with shells had obtained less short rounds or the same number of rounds short and over the target. In the meantime the sections charged with shells fired for effect and filled in the pauses, until the burning time of the fuze had been set. Then the whole battery shifted to shrapnel fire, adopting the height of the sight that had obtained the greater number of short rounds : if the number of the rounds short and over was the same, the height was narrowed by 1 graduation. In either case the fuze was set for a normal burst. To control the interval of burst, one section fired a verifying salvo, changing the elevation by 2 graduations. If no round fell over the target, the elevation was changed again by 2 graduations. When one or more rounds fell over, the guns kept the long limit of the bracket or narrowed the elevation of the verifying salvo by 1 graduation.

    directly with shrapnel : it was regarded as exceptional, since it required low bursts, that might result in a lot of graze bursts, that were not only absolutely ineffective, but also of little value for the observation. It was made by section (two guns) exactly as with shell, excepting that in this case two observations were made for every height of the sight. The bracket could be reduced up to 2 graduations also by means of a single observation, if the other was lost, but the repetition of the limits and the groups should always result from the correct number of the observations, even if it caused a great waste of ammunition. After having fired the group of verifying shots, the whole battery shifted to shrapnel fire simultaneously. If the number of the rounds of the group over the target was less or equal to the number of the short ones, the height of the sight was kept unchanged or narrowed by 1 graduation. The interval of burst was verified as above, with fuze set at low burst to facilitate the observation. Shifting to fire for effect, the burning of the fuze was shortened by 0.1-0.2 seconds, but the trajectory should never be raised.

 

The adjustment in direction (определение на отклонението) was required to overcome the effect of wind and drift. In this case the sections commanders made the changes in deflection according with the firing tables and taking into account the slope of the axis of the guns and the direction and power of the wind. With cross wind the correction was made by the battery commander. The deviation was regarded as correct when the deflections of the shots on the right and on the left were almost the same.

 

The adjustment in height of burst (определение на височината на пръскане) was made observing a group of shrapnel shots having the same fuze setting. The height was regarded normal when :

    at close range not less than half of the burst were low, and no burst were on graze;

    at medium range at least one burst of every salvo was low, and not more than one burst every two salvos was on graze;

    at long range there was no low burst in a salvo, and only one burst at most every battery salvo was on graze.