Once a Week (magazine)/Series 1/Volume 1/English projectiles - Part 3
Page:Once a Week Jul - Dec 1859.pdf/58 Page:Once a Week Jul - Dec 1859.pdf/59 so that the whole strain between the shot and the breech in the act of propulsion came on the screw threads, and it is said that two shots could not be tired without straining the threads, and so loosening the cylinders. This might perhaps be remedied by increasing the number of the bolts, but there is another difficulty.
The proportion of weight between shot and barrel in an American hunting-rifle is about one to four hundred. In an English 64 -pounder cast gun it is about one to one hundred and fifty. In Mr. Mallet's gun the proportion is, shot one, gun forty. If therefore this gun were made perfect in other respects, the weight would have to be made up by the carriage, or the earth, and if placed on a vessel it would have to be placed on buffers of caoutchouc, or it would probably damage the vessel. It would be quite right to carry forward this experiment, increasing the numbers of the bolts, diminishing the diameter and using a cylindrical instead of a spherical shot, thus reducing the diameter, with the same quantity of explosive matter and dead weight. The only reason for making the gun in parts is to attain facility in transit. New discoveries, to which we shall presently allude, have settled the question as to procuring malleable iron in any sized mass we may desire.
While these experiments were going on at the expense of Government, Mr. Armstrong of New- castle, no regularly bred but a positively born engineer, was experimenting on his own account, possessing all the wherewithals, abundant means and a well-fitted engineering factory in prosperous trade. With good common sense he took the best thing that was next to him — the rifle — and set to work to enlarge it. He adhered to length and weight with a small diameter of bore, and he elongated his shot and covered it with soft metal to fill the grooves by expansion in forcing through. The grooves were a serious consideration, and to ensure an easy fit he filled the barrel with small W shaped grooves alternating with similar ribs, precisely like an old French plan used in the pistols of the elder Bonaparte, as may have been observed at Madame Tussaud’s Exhibition. To load a gun of this kind from the muzzle was not conveniently practicable, so he determined on breech loading. The plan he chose is that used by the Chinese, and in the East Indian jingals. A longitudinal piece of metal with a handle like that of a saucepan-lid is inserted in a slit on the upper side of the barrel cut in to the bore. At the back of the breech piece the bore is continued through of a larger size, and a hollow screw, the hollow being the size of the bore, is screwed into it. The object of this hollow screw is to pass the charge through it into the barrel, and then the breech- piece being put in situ, the screw is screwed up against it to tighten the barrel, and prevent the escape of gas. This is an exceedingly ingenious arrangement, and effective for a small-barrel gun, and not more likely to get out of order than the ordinary screw breech of a fowling-piece or musket, but if applied to larger-sized guns it is doubtful if so heavy a strain on the screw threads will be found to answer. The weakness is of the same kind as the threads of the bolts in Mallet’s gun.
In the manufacture of these guns of wrought- iron, Mr.— now Sir William — Armstrong has also shown good sense and judgment. He combines the processes well known in ordinary gun-barrel making. First he takes a welded tube made as musket barrels are made, and round that he wraps a spiral riband of iron in the mode in which fowling-piece barrels are made. A second riband of iron is wound spirally in the opposite direction, and the whole is welded together. While this is done on a small scale, there will probably be little difficulty in success, but the success in very large guns is dubious. But neither is the non-success of any importance, as guns of any size may now be produced at pleasure.