The attention of foreign governments has been called, in the past few years, to the development of small arms. A great many proposed changes have been discussed, and amongst them, that of reduction of calibers.
On this subject little has been said in this country, and that little, as might have been expected, has generally been adverse to the newarm.
The Hebler bullet is steel covered.
The data need a word of explanation. The bullet of the Hebler rifle has beyond a doubt attained a velocity of 1968 f. s., but there is no confirmation of this by official trial ; consequently in all the calculations the velocity used is 1850 f. s. In no way does this article uphold the Hebler as the best small arm of reduced caliber, but, owing to the exhaustive trials held with this rifle, data were obtainable. It may be mentioned here that the Fieri (cal. .323) and Lobell (cal. .307) have attained a velocity of over 2000 f. s.
The following results have been computed by ballistic tables, using Mayevski's laws of resistance of the air. The arc of the trajectory has been considered equal to a chord, and for purpose of comparison this will be sufficiently accurate; the assumption will, however, be prejudicial to the Hebler, for its trajectory is flatter. The final velocity and energy for each range will be relatively greater and the time of flight less for the Hotchkiss.
By reference to the table it will be seen that the final velocities of the Hebler at all ranges are greater than those of the Hotchkiss. Column n, shows the total energy to be nearly the same at all ranges for the two rifles, but there is little inference to be drawn from it. The work wanted of a small arm is penetration ; the energy per unit of cross section or per unit of circumference is a fair measure of penetration, and columns HI. and V. show a great superiority for the Hebler. It will be noticed above that at the muzzle the penetration of the Hebler is twice that of the Hotchkiss : at 2700 yards, 2.75 inches, as compared to 3.7 inches at only 1200 yards. The times of flight will be referred to later in connection with drift and retardation. Perhaps the greatest advantage of all possessed by the Hebler is a flatter trajectory. A flat trajectory means greatly increased dangerous space, larger under- and over-estimates of the range allowable, and generally less care in the adjustment of the sights (not less care in sighting), and in active service this would not be an unimportant item.
The full benefits of this increased dangerous space would be most felt, perhaps, in cases of a night attack, or in any case where the objects were obscured. An increase of the point-blank range is, of course, of the greatest value. This subject has been so well ventilated, and the great advantage of a large dangerous zone is so well known, that no farther mention of it will be made in this paper. The above diagram, representing the trajectories of the Hotchkiss and Hebler rifles for a range of iioo yards, shows the great superiority of the latter rifle in this respect.
Now, it is held by many that these advantages follow from the better motive force in the Hebler, or, in other words, from the improved Hebler cartridge, either in its composition or shape. It has even been stated that this motive force is over double that of the American rifle. This statement, unless carefully sifted, would give the impression that reduction of caliber has very little to do with the better ballistic results given by the Hebler rifle, and that by improving the American cartridge we could get the same results with our large caliber.
Therefore the force of the Hebler explosive is not materially different.
The quantity f used in the formula may be defined as the pressure per square inch developed by the gases evolved from unit weight of the explosive, the condition being that these gases occupy unit volume.
This quantity f, then, can be changed only by altering the proportion of ingredients, or changing the ingredients altogether.
The conclusion to be drawn, then, from the above result is that the composition of the Hebler charge is very similar to our own, or, if there is a change, very litde if any additional velocity is gained thereby.
Where all the powder is burnt in the gun, the shape of the grain has no influence on the velocity. For any given weight of charge and length of barrel there will be a given volume of gas evolved, making a certain number of expansions ; therefore the work done must be constant ; hence the velocity will be constant with a bullet of fixed weight. The above formula for velocity, taken from "Velocities and Pressures in Guns," Vol. XIV., No. 2, page 402, Proc. U. S. Naval Institute, as can be expected, contains no coefficient depending upon the form of the grain. The reason for this change of shape is obvious : it is to get a large mean pressure with a small maximum. The Hebler charge is a pierced cylinder of compressed powder. All other elements of loading being the same, the maximum pressure varies directly as a coefficient depending on the form of the grain (whether the powder is all burnt in the gun or not) ; this quantity, for a spherical or cubical grain, or for any irregular shape approaching them, is 3. For any pierced cylindrical grain burning from inside and out, this coefficient is 1 + x, where x is the ratio of the least to the greatest dimension of the grain. For the Hebler charge this is not quite 1.2. If the grain burns from the inside alone, the coefficient will be still smaller. The calculated pressure of 83 grains of loose powder in the Hebler rifle is about 34,000 pounds per square inch, loose powder being considered spherical in shape measured pressure in the Hebler gun is 7.32 tons, or about 16,350 pounds per square inch.
It has been stated that if the motive force were increased in the Springfield (caliber .45) in the same proportion that now holds in the Hebler, the initial velocity of the former would be 2008 f s. Let us grant for a moment (but only for a moment) that this is so. The recoil would be entirely too violent, approximating 22 ft. -lbs., or twice what it now is. Suppose, again, we could give the Hotchkiss bullet a velocity of 1800 f. s., the recoil in ft.-lbs. with our 405-grain bullet would be 19 ft.-lbs. It is at present about 11 ft.-lbs. It is a very evident fact that the initial velocity cannot be increased with a limited recoil without increasing the weight of the rifle, which is already at its maximum limit. Army officers, it is believed, generally concede that the present recoil (11 ft.-lbs.) is quite large enough. Recruits suffer with this, and even trained soldiers have been more or less badly knocked up after a skirmish drill where a given number of shots must be fired while advancing a certain distance.
Another objection raised to reduction of caliber is increased drift due to side wind, owing to lightness of bullet. In the Proceedings of the Royal Artillery Institution, March, 18SS, appears a paper, translated from the German by Major W. McClintock, R. A. An account is given therein of experiments made in England with rifles of various calibers, the result of which was the abandonment of trials with the smallest caliber. The paper then says, ''A further reason for this decision lies in the fact that with the smaller caliber the bullet has a less surface of longitudinal section, and therefore the greater effect of a side wind was feared (!)" Major McCIintock appends a justly sarcastic foot-note, "there is something wrong here."
Let it be remembered, before investigating this point, that a known error can be compensated.
The strongest argument against reduction of caliber is loss of power, and as long as we cling to worn-out ideas this cannot be disputed. This loss of power is due to the fact that to keep the pressure per square inch down to the elastic strength of the metal of the barrel, the total effective pressure on the base of the projectile must be lowered. But those who have argued against reduction of caliber have generally made the most out of this. It is not always mentioned that (1) keeping the weight and length of the barrel constant, the thickness of the smaller caliber rifle is greater, or (2) the weight and thickness being constant, the length is increased.
1st. Considering the mean thickness of the Hotchkiss as 0.22 inch, that of the Hebler would be 0.264 inch. The pressure in the former rifle is 19.000 lbs. per square inch.
2d. If the weight and thickness are constant, the length can be increased about one fifth. The muzzle energy is Pl\ therefore increased travel means more work. It means a great deal more at the present day ; it admits of the use of a more progressive grain. Again, a larger charge can be burnt, and the velocity, it must be remembered, varies as the f power of the charge. This increased weight of powder can be used without undue strain by changing the shape of the grain, as has been done in the Hebler cartridge.
Fouling of the bore is still another disadvantage claimed by the believers in large calibers. Professor Hebler maintains that the steel covering polishes the bore, thus enabling the barrel to better resist the chemical action of the gases, and prevents leading. He fired 1500 rounds and there was no wear on the grooves.
Actions in the future will begin at greater ranges, small -arm fire commencing at from 2000 to 2500 yards. Such being the case, the question of supply of ammunition assumes even greater proportions. The weights of the Hotchkiss and Hebler cartridges are in the ratio 521/640 = .81, and it must be remembered that this ratio is still less with other rifles of .45 caliber, 500 grains being the usual weight of bullet for that caliber. Machine-guns must carry at least 10,000 rounds of ammunition, and the saving in weight is very considerable.
The following is an abstract from an article by Lieutenant Beehler, U. S. Navy, entitled "Recent Progress in Small Arms":
"Experiments on animals demonstrated that the wound caused by the Hebler bullet was much less serious than that from others. The Hebler bullet makes a clean hole, while others make ragged and splintered holes, so that even if vital parts are not struck, the wound made remains serious for years. In one case a man shot by Hebler bullet in upper left arm entirely recovered in three months though he was hors de combat for two months."
Nearly all foreign powers have made extensive experiments and some have already adopted small arms of reduced caliber. Portugal has the Gu6de, cal. .323, and a bullet weighing 264 grains ; the proposed rifle for Italy is the Freddi (recoil), cal. .315, weight of bullet 225 grains ; Sweden, the Jarmann, cal. .397, bullet, 337 grains, but only 1000 of these arms have been issued, as many demand a further decrease of caliber. In France it appears that the introduction of the Gras-Lobell (?) rifle, cal. .315, was advocated, and the manufacture of this arm was to have begun at the Tulle factory, but owing to the uncertain state of Europe it was deemed inadvisable to commence the re-armament of the infantry, which would take about three years. The largest caliber at present in use abroad is the .433, and all the countries using this are on the verge of reduction of caliber. The latest order for rifles of reduced caliber has come from Austria. This order is for a number of Maxim automatic machine-guns, caliber 7 mm. = .28 in.