The objects to be aimed at in devising rifle balls are two— to maximize the force of the powder and to minimize the resistance of the atmosphere. The explosive force of the powder is diminished in proportion to the looseness and to the unsteadiness of the ball in the barrel. If the ball is loose, part of the explosive force (called windage) passes off at the sides, and another part is neutralized by the friction between the barrel and the ball, which, in its progress, rolls instead of sliding along it. The rolling motion is effectually prevented by the process of rifling, which holds the ball forcibly in the same position until it passes from the muzzle; and the windage is avoided by hollowing out the bottom of the ball in such a manner that, when the explosion takes place, the edges are driven outward by the powder, and completely fill up all interstices between the ball and the barrel. In the Minié balls, this operation was performed by a small iron cup, somewhat larger than the hollow, and was placed at the bottom of it; but experiment showed that the violence of the explosion was such that the cup was often driven right through the ball, leaving it wedged immoveably in the grooves and barrel of the rifle, in the shape of a long film of lead—thus rendering the gun completely useless for a considerable time.
When the bullet leaves the barrel, the principal difficulty which it meets with arises from the resistance of the atmosphere, and the degree to which that can be reduced depends principally upon the form of the ball. After numberless experiments, Colonel Jacob arrived at the conclusion that the best shape was one somewhat resembling that of an acorn with a very sharp point, and a cylindrical base forming one-fourth of the whole length. The base has four projections, which fit into the four grooves of the barrel, and the grooves make five-sixths of a complete turn in the pattern rifle proposed by the inventor for the use of the army. From its peculiar shape, the ball offers so little resistance to the air; and the grooves of the barrel keep it so accurately in its proper position, that though it weighs twice, as much as a round ball of the same calibre, it requires only half its charge of powder, and ranges with great accuracy for 1400 yards. One great advantage of the use of these balls is, that the gun can be loaded with even less trouble than an ordinary musket.
The most remarkable, however, of Colonel Jacob's achievements consists in the discovery of a special purpose to which these balls can be applied. By casting them with a deep hole in the fore part, into which is fixed a copper tube, filled with percussion powder and pointed at the end, they become percussion rifle-shells, which Colonel Jacob describes, with much apparent justice, as “the most formidable missile ever invented by man.” They explode on striking, and the force of the gun, and its accuracy of aim are such, that it would seem that a few riflemen might henceforth make it impossible for field artillery to come into action. At a trial at Kurrachee, an ammunition waggon was made out of an old cart, in which four ammunition boxes were placed, packed in the ordinary way with round shot, cartridges, &c. Three of the four boxes were blown up, and the cart destroyed, from a distance of 1200 yards, by Colonel Jacob and three other gentlemen in a very short time. Captain Gibbard blew up one box in seven shots, and Colonel Jacob blew up another in five. On another occasion, the same gentlemen, under unfavourable circumstances, blew up a large box of Powder, placed on the ground at no less than 1800 yards distance. The rifle with which this feat was performed was a small double-barrelled one of 24-gauge. The force with which the balls are thrown is perfectly wonderful:—
‘At Kurrachee on the 26th September, 1856, a 24-gauge iron-pointed ball, fired with a charge of 2½ drams of powder, at a distance of twenty-five yards, penetrated clean through eighteen deal planks, each three quarters of an inch thick, and smashed itself all to pieces against stones on the other side.The percussion shells penetrated four or five inches into walls made of sun-hardened bricks, and exploding, left deep holes in them. Colonel Jacob says, that if the same principle were applied to cannon, he “is deliberately of opinion that a four-grooved rifled iron gun, of a bore of four inches in diameter, weighing not less than 24 cwt., could be made to throw shot to a distance of ten miles, and more, with force and accuracy.” The magnitude of the results which he has already obtained forbid us to look upon this as an idle or unfounded boast.
Again, at Kurrachee on the 29th September, 1856, a 24-gauge iron-pointed ball, with a charge of 2½ drams of powder, was fired at twenty-five deal boards, each a little more than three quarters of an inch thick, the whole thickness of all the boards together being twenty inches; the boards were packed close, one behind the other, and wedged fast into a box. The rifle was fired at twenty-five yards distance. The ball penetrated clean through the whole twenty-five planks, and buried itself its whole length in a block of hard wood 2½ inches thick, which was behind the mass of boards, breaking this block into two pieces.’
It is curious to speculate on the importance of such discoveries as these. That it must be very great has been made abundantly clear by our experience in the war with Russia. Colonel Jacob anticipates from it the most brilliant consequences. He has the most enthusiastic estimate of the “noble nature,” both moral and intellectual, of English troops; and he considers that, by enlisting into the army a much superior class of men to those whom we at present employ, and by arming, them with the weapons which he has invented, a force numerically small, but carefully and individually trained, might be formed, which would be almost invincible. He looks forward to a great increase in the influence of personal daring and resource on the fate of battles, as a natural result of the employment of an arm which requires so much skill and nerve for its proper use; and he thinks that close formations either of infantry or of cavalry will be almost at the mercy of well-trained riflemen, advancing upon them in open order.
No doubt a man rides his own hobby pretty freely, and we fear that, notwithstanding the real importance of Colonel Jacob's discovery, he may be a little tempted to lay too much stress upon it. Still, we feel that his language and his anticipations are generous and manly; and we should be rejoiced to see the habit of using the rifle, as our ancestors used the bow, added to the number of English national sports. Rifle-shooting is universal in Switzerland, and even school-boys are trained to take aim with a kind of cross-bow, which is far from being a mere toy. With all the goodwill in the world, our means of obtaining manly exercise are daily being refined away, and it would be a great piece of good fortune if, by one and the same invention, we could increase our military power and add to the number of our national amusements. It is a circumstance which deserves passing notice as a curiosity, that Jeremy Bentham was one of the first persons to point out the political value of the rifle as an arm for citizen levies, and that the learned author of Fearne's Contingent Remainders took the lead, not merely in confuting Lord Mansfield, but in the invention of long-range, small arms.
Saturday Review, February 28, 1857.