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cap, and Sharp's rifle also is without one; but in each case a copper disk is substituted for it, and as there is merely an alteration of form, they can scarcely be said to be exceptions.
We may, therefore, assume that in all cases our modern guns are made so that the charge is exploded by means of a cap or disk containing fulminating powder, and exploded by means of percussion. In this point, therefore, there is little difference to be found in the principle adopted, and we must look further to discover the particular element in which the various guns now in use differ from each other. We find them to consist chiefly of, first, the original percussion gun, which has been in general use among sportsmen for about forty years; secondly, of the French crutch gun, introduced into England within the last four or five years, but known on the Continent for about twenty years; thirdly, of Lancaster's additions to this; and fourthly, of Needham's needlegun. There are minor points of difference adopted by gunmakers in the two first divisions; but the two last, being patented by their respective inventors, are each of one pattern only. Now, among all these four the barrel is nearly the same, and the charge is fired by means of a percussion cap or disk; but, while in the first this charge is introduced by the muzzle, in all the three last the breech is opened for its insertion and then closed again by a mechanical contrivance. Hence, in the list of the various shotguns of the present day, a distinction is now made between muzzle-loaders and breech-loaders, and these must be separately examined before their merits can be compared, with a view to ascertain how nearly each of them conies to the standard of efficiency which is desired. In order to ascertain what that is, we must first consider what are
THE DESIDERATA IN THE SHOT-GUN.
It is found by experience, as far as our present knowledge goes, that a gun can only be made to combine a certain amount of strength with regularity of pattern. By a particular method of boring its cylinder, it is comparatively easy to obtain either of these objects, but the other cannot be added without a sacrifice of the first in some degree. Hence it is the practice of our best makers to bore their guns so that at from forty to sixty yards they shall give such a pattern on the target as will prevent the escape of a partridge or grouse, and at the same time drive their shot with as much force as possible. These two points may, therefore, be considered as the two essentials; and, in addition, it is considered desirable to avoid encumbering the sportsman with a tool which shall be too heavy for him to carry without fatigue, or, with one whose recoil shall be unpleasant to him from its severity. A practical man knows that a heavy gun shoots better than a light one, and that the recoil must to a certain extent be in proportion to the force with which the charge is driven forwards; but he also knows that either one which is too heavy, or which recoils too much, even if its shooting is very good, is wholly useless to most sportsmen. He therefore endeavours to make his guns with the following good qualities, which are those that are generally regarded as the requisites for a shotgun. These are, first, a good pattern on the target made by them at forty and sixty yards; secondly, as much force in driving the shot as possible, in combination with the first quality; thirdly, lightness as far as is compatible with safety and good shooting; and fourthly, the absence of such recoil as is unpleasant to the shooter.
Every gun may, of course, be made clumsily or the reverse, but the maker who does not turn out his productions in a workmanlike manner must be rejected on that account, since there is no excuse for him in this respect. All should be well balanced and the parts accurately fitted together, while the mechanism of the locks, &c., should be of the most highly-finished kind consistent with the price. A cheap gun may shoot strongly and make a good pattern, but its parts will be seen to fit badly and its locks will be sure to be faulty. Hence it soon wears out, and, in addition to its want of safety, it will generally be found to be the dearest in the end. By the word cheap I mean the opposite extreme to the high price which is charged by our fashionable makers, and not the medium charge made by our best provincial gunmakers, who are content with profits which would not support the expensive establishments of some London makers. It is
essential to the safety of the sportsman that he should select a tradesman who has a character to lose, and who is not driven by necessity to risk the lives of his customers by underselling his rivals. On this point every man of any prudence will take care to protect himself; but if he will only be guided by the rules of common sense, and by his practical knowledge of human nature, he is just as likely to be furnished with a safe gun, and a good shooting one too, at one-fourth below the top price, as if he paid that sum to one of the most fashionable makers of the day.
The final boring of a gun—that is to say, the operation which determines the exact shape of its interior, will vary greatly according to the materials and shape of its breech, and to the length of the barrel. None are made of a truly cylindrical shape, and it is usual to "open” or “relieve” them, or sometimes both processes are adopted. By opening is to be understood the formation of a slight cone with its base at the breech; and by relieving, the production of a cone with its base at the muzzle. The exact proportion of these parts is, however, one of the secrets of trade, and almost every gunmaker professes to have a plan of his own, which he considers superior to all others. The old flint gun was both opened and relieved; the detonator is generally also slightly opened; but a considerable degree of this causes a good deal of recoil, and some makers only relieve their guns. I believe that there is no absolute certainty in the practice of boring, and that in almost every case some attention will be required after trial. This is what is called “regulating the gun, and hence we so constantly see gunmakers shooting at an iron plate to enable them to ascertain what is to be remedied. If the gun spreads too wide it is relieved, while if it has not driving power enough, it is opened till it performs to the satisfaction of the trier.
The rifle consists of an iron or steel tube similar in its external form to that of the shot-gun, but grooved internally in a spiral direction, so as to make the ball which it carries revolve or spin around the long axis of the barrel when continued forwards. These grooves may be narrow or wide, deep or shallow, and of any number from two upwards. In the oval-bore, as it is called, the rifle appears at first sight to
be similar to smooth bore, but it really is merely a twogrooved rifle with the edges of the grooves rounded off. It is unnecessary, however, here to go into the details of these different methods of grooving, which will be found fully described in the Fifth Book.
ON THE ACTION OF GUNPOWDER AND OTHER
GENERAL REMARKS-ACTION OF THE POWDER ON THE PROJECTILE
MODE OF DETERMINING ITS VELOCITY - EPROUVETTES — RESISTANCE TO THE MOTION OF PROJECTILES THROUGH THE AIR - RECOIL COMPOSITION OF GUNPOWDER AND GUN-COTTON, AND THE MATERIAIS USED FOR FIRING THEM BY PERCUSSION.
ALTHOUGH much has been done within the last few years in improving the machinery by which bodies are projected through the air, yet little has been discovered since the days of Robins and Hutton, in reference to the principles upon which they act. Indeed many so-called novelties of 1858 and 59 are merely old inventions warmed up, and this is more especially the case with regard to Mr. Lancaster's oval bore, which was described in the clearest language in the year 1808, as will be fully shown in the proper place. The following propositions are chiefly taken from the pages of the celebrated Robins, who is still accepted as the highest authority on the subject.
Gunpowder when exploded produces a permanently Elastic Fluid.—If, says Robins, a red-hot iron be included in a receiver, and the receiver be exhausted, and gunpowder be then let fall on the iron, the powder will take fire, and the mercurial gauge will suddenly descend upon the explosion; and though it immediately ascends again, yet it will never rise to the height it stood at before, but will continue depressed in proportion to the quantity of powder which was let fall. The same fact may be shown when gun
powder is fired under the ordinary pressure of the air, as for instance in a glass tube, the mouth of which is immersed in water, leaving only space enough for the powder at the top. If in this state the powder is fired either by a burning-glass or by galvanism, it will be found to displace water to the extent of nearly two hundred and fifty times its bulk, and as soon as the gas produced by the explosion cools to the temperature of the surrounding air it ceases to contract, and remains a permanently elastic fluid.
Modes of determining the Quantity of this Elastic Fluid produced from the Explosion of a given Quantity of Gunpowder. - Different qualities of powder produce different quantities of gas, and therefore in any calculations which are made public, it is necessary to specify the powder which has been used. Most of that sold now is probably far superior to the powder with which Robins made his experiments; but, nevertheless, they approximate to the truth sufficiently for our purpose. He used the Government powder of his day, which was, I have reason to believe, not within thirty per cent of the strength of the Government powder of 1859. He says that “1 drachm of powder avoirdupois, on explosion, sinks the mercurial gauge 2 inches ; and the mercury in the barometer standing at near 30 inches, 15 drachms avoirdupois, or 410 grains troy, would have filled the receiver with a fluid whose elasticity would have been equal to the whole pressure of the atmosphere, or the same with the elasticity of the air we breathe; and the contents of the receiver being about 520 cubic inches, it follows that 15 drachms of powder will produce 520 cubic inches of a fluid possessing the same degree of elasticity with common air; whence an ounce of powder will produce near 555 cubic inches of such a fluid."
But in order to ascertain the density of this fluid, we must consider what part of its elasticity at the time of this experiment was owing to the heat it received from the included hot iron and the warm receiver, and this is estimated by Robins at about one-fifth of the whole, which brings 555 down to 444. And this last number represents the cubic inches of elastic fluid, equal in density and elasticity with common air, which are produced from the explosion of 1 ounce of powder; the weight of which quantity of fluid, according to