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1036 In Germany the cardboard-tube method, on the contrary, answered very well indeed with ammonal explosives. The explanation lay in the very different design of the Austrp-Hungarian base-fuzed shells, which made them very liable to accident when the explosive was badly settled in the shell cavity. However, trotyl, ekrasit and 60/40 amatol remained the most satisfactory explosives from the point of view of the manufacture, and hence the least open to objection.

As substitute explosives, ammonium-nitrate explosives and chlorate explosives were used. Among the former, dynamon was used in cast- iron shells, for reasons of safety as already explained. The scantiness of the smoke produced and the fact that ignition depended upon the density of filling caused this substance to be regarded with disfavour. However, dynamon and (in Germany) a number of similar safety explosives were used in trench-mortar shells and grenades, and for engineer munitions, with good results.

The chlorate mixtures, put out under various names (chiefly in Germany) and intended for various military uses, soon disappeared again in consequence of numerous disasters, which could be traced to over-sensitiveness on discharge, filling dangers, and their liabil- ity to disintegrate. The perchlorate explosives were satisfactory as regards safety. They were used with good results for certain trench- mortar bombs, but only in Germany. A radical measure of economy was found in the use of " economical filling." The portion of the shell cavity nearest the fuze was filled with the selected explosive and part of the remaining space with pitch. By the use of very powerful ignition this process gave far better results than might have been expected, but it was never used on a large scale.

Notwithstanding these comprehensive measures the lack of ex- plosives, which, at all events in Austria-Hungary, was chronic, greatly hindered the supply of artillery ammunition, almost as much in fact as did the difficulties of propellant manufacture. Both deficiencies were due to the backward state of the chemical industry in that country. Although the needs of Germany were very much greater than those of Austria-Hungary she was always able to re- spond to them much more quickly.

Bore Explosions. Special care was devoted to obviating the bore explosions which were so disastrous both from the point of view of the command and that of the troops. As has been said (except in the case of the unsatisfactory cast-iron shells), these could very seldom be attributed to the shell-material. In the case of very long high- pressure guns it is possible that shells on the high limits of tolerance were jammed by the action of the so-called breath of the barrel. More sources of defect were naturally to be found in the fuze, which must inevitably contain a very powerful igniting composition. In Austria-Hungary detonators were regarded as dangerous. The fear does not seem to have been justified, provided they were properly placed and secured, and due precautions observed, but they are yet another source of weakness in mass-production. At all events, there were few bore explosions with the Austro-Hungarian pressed-steel nose-fuzed shells, which had very simple fuzes without detonators - fewer, in fact, than occurred with the German shells. The Austro- Hungarian base-fuzed shells had the defect that absence of a deto- nator necessitated the adoption of a long exploder-gaine, which greatly increased the difficulty of securing the explosive charge against the shock of discharge. Herein also lay a cause of the above explosions, which at one period were occurring with disquieting fre- quency. It was at first very difficult, especially with toluol-ammonal fillings, to fix the compressed blocks to the shell-wall firmly enough to prevent their setting back, and disturbing the ignition arrange- ments. Later on, these causes were discovered and almost entirely eliminated.

These special factors being left out of the question the number of bore explosions cannot be considered to have been abnormal, either in Germany or Austria-Hungary. Inpeace-time it was reckoned that in every 10,000 H.E. rounds there would be at least one unprevent- able " premature." For example, during the Austro-Hungarian gun- practice in the years 1912 and 1913 the percentage was as high as 0-04 ; whereas in July 1915, a particularly bad month, the percentage was only 0-023 and in June 1915 only 0-012.

These explosions may be ascribed chiefly to the impossibility, in quantity production, of superintending the work so minutely as to eliminate altogether the possibilities of error in the manufacture of the fuzes, the thorough sealing of the shell-bases, and the filling of the bursting charge. The proper handling of the ammunition, in the depots, during transport, and in loading, was also an important factor in safety.

Cartridge Cases. Except in a few old types of gun the Austro- Hungarian artillery always used cartridge-case obturation. All flat-trajectory guns of small calibre used fixed ammunition. All mortars and howitzers, and especially all large calibres, had sep- arate loading. The idea that this unfavourably influenced the rate of fire had led to the attempt, in peace-time, to use fixed ammunition for light howitzers. While the fore part of the case was joined to the shell the nether part was detachable. Later on this method of load- ing fell into disfavour because of its complication. When the demand arose for reduced charges for field guns, in order to spare the guns and also to adapt them for firing from concealed positions, this prob- lem was taken in hand more seriously, and in Austria-Hungary a very simple and satisfactory contrivance was found, though never made in large quantities.

At first the cartridge cases were always made of sheet brass by drawing and pressing. The cases were recovered after firing and used again, re-manufacture seldom being necessary; but although this salvage enabled a large part of the need of cartridge cases to be met, it soon became necessary to resort to substitutes, owing to the universal lack of brass. At first the deficit was made good by the use of iron bases and brass sides, joined together in a very simple manner. Generally speaking, cartridge-case obturation proved much more trustworthy in practice than was expected. In fact the two- piece construction eliminated one of the greatest sources of defect in the single brass case, i.e. the weakness at the bend between the base and the sides. The danger of burning through in this region was insured against in the design. The kind of material used for the base was not- of much importance, cast-iron proving quite satisfac- tory. In the end iron-plate was used for the cylindrical part, even up to the heaviest calibres, except for use in long-range guns. Conspicuously good results followed, especially in Austria-Hungary, where, finally, a simple case of sheet-iron bent round, with an inward flange at the lower end, was used for the cylinder. It would stand being fired from 10 to 15 times without re-manufacture. In Ger- many, also, iron shell cases fully satisfied the requirements, and could be fired 5 or 6 times.

These iron cases replaced the brass ones altogether. The manufac- ture was simpler. Only the junction of base and shaft needed careful working. Bruises and dents did not matter in the rolled cases; they were smoothed out in firing by the expansion of the gases.

The prevention of rust of course was a difficulty ; but this was less important in war, owing to the short time that elapsed before the shells were used. Excellent results were obtained by dipping the cases in oil raised to a temperature of about 100 C., and repeating the process several times. The examination in Austria, in June 1921, of ammunition which had been stored without any special care showed that almost all the cases so heated were still serviceable.

The powder charge was inserted into the cartridge cases in bags of raw silk. As this expensive material soon became scarce, sub- stitutes had to be employed in charges made up of separate elements (with cartridge cases the bag was omitted). Artificial silk proved a satisfactory substitute. Paper substances were also successful in the parts lying away from the primer. No exhaustive trials to determine the chemical effect of the powder on paper were carried out.

Propellant Powder. The smokeless powder used in the German army as a propellant was almost invariably a nitrocellulose powder. Nitroglycerin was used only in small quantities. In Austria-Hungary, on the contrary, pure nitrocellulose powder was the propellant of small-arms ammunition only. All other propellants were nitrp- glycerin powders containing a high proportion of the nitroglycerin (up to 40 %). The particular composition and the form varied with the purpose in view and the gun concerned.

The Austro-Hungarian guns had in general a smaller chamber space than the German, with a greater energy-content in their powders. The higher combustion temperature of the nitroglycerin and the stronger flash had an extremely bad effect on the interior of the bore, especially when substitute materials were used in the composition of the powder. The use of this powder in the field guns was the main cause of the great wastage in these compared with the German field guns. The Austro-Hungarian steel-bronze guns re- sisted better; not so, however, the steel guns which came into use because of the scarcity of metals, and of bronze in particular. When, later, a change was made to a powder poor in nitroglycerin, the unsuitable size of the chamber created great difficulties in determin- ing the proper charges.

No new powders were used or produced during the war by either Power. Some simplification of processes was all that was effected. But the German chemical industry energetically attacked the prob- lem of producing the basic products used in powder manufacture, and in this domain new combinations were made and new ways opened. Among partial novelties may be reckoned the development and improvement effected in the preparation of ammon powder, which had been experimented with in Austria before the war, and even used in her navy for a short time.

The use of substitute raw materials had a considerable effect on the production of powder, and some effect, also, on the results obtained by its use. Special importance attached to the nitration of wood cellulose as influencing the quality of the powder.

At first it was impossible to get rid of the papery consistency of the wood cellulose, but, later, direct nitration was successful. Variation in the viscosity of the wood cellulose or in the preparation of nitro- gen-content necessitated variations in the dimensioning of the pow- der. The unequal nitration of the cellulose was particularly marked and produced differences in the degree of nitration which led to un- equal gelatinization and a varying energy-content.

The nitrate difficulty disappeared when it became possible to obtain nitrogen from the air in large quantities; but the victory over the alcohol, ether and acetone shortage was won with more dif- ficulty. These substances were required for gelatinization. The acetone obtained from wood distillation was mostly produced in Austria-Hungary, which partly supplied Germany.

In consequence of the great demand other products of wood dis- tillation had to be brought into use, and the purity of the acetone suffered. Instead of the solvent method, therefore, the roller or