Gunnery in 1858: Being a Treatise on Rifles, Cannon, and Sporting Arms / Explaining the Principles of the Science of Gunnery, and Describing the Newest Improvements in Fire-Arms

by William Greener

Boring and grinding gun-barrels generally take place under the same roof; the borer occupying a very small shop, the grinder a large one. Two men and two boys are generally found in a shop. There are four benches, to each a spindle, in which there is an oblong hole to receive the end of the boring bit. The barrel is secured on a sort of carriage, which is at liberty to traverse the whole length of the bench. A boring bit is then selected of suitable size; it is put into the spindle, and the point introduced into the end of the barrel. A sort of lever is then taken and hooked on to a kind of staple, or a piece of hooked iron (a number of which are fixed in one side of the bench the whole length), and passed behind the carriage to force it up to the bit; this is removed and fixed again, until, by forcing up the carriage, the boring bit has passed through the whole of the barrel. During this operation a stream of water is kept playing on the barrel to keep it cool. A bit, of larger dimensions, is next introduced and passed through; then others of still larger dimensions, until the whole of the scales or blacks are entirely bored out; or until the barrel has become so large in the bore, as to preclude any further boring with safety. If the scales are of great extent, the fault is the forger’s, and the loss will consequently be his. If the barrels be found perfect, they are sent back to the filer, or he comes to inspect them, in order to ascertain whether they be perfectly straight in the inside; if not, to make them so.

The necessity of great care and attention to this point, must be very obvious; for, if not perfectly correct at this stage, it will require more skill and time to get it correct afterwards than the generality of barrel-makers are inclined to bestow.

When the inside has been found to be all right, the barrel is ready for grinding. Many barrel-makers turn their barrels entirely by self-acting lathes, and thus obtain a correct taper from breech end to muzzle. Experience has clearly convinced us that this is not the best shape, but slightly hollow towards the muzzle is preferable, as additional weight there is decidedly injurious, and the shooting of barrels of lighter construction is decidedly better.

The generality of Birmingham barrels are ground to the size required on large stones, which revolve at a terrific rate. The skill acquired by many of the workmen is astonishing. Over and over again, have we seen barrels coming from the mill put into the lathe, and found almost as true as if they had been turned. They have a method of allowing the barrel to revolve in their hands at half the rate of the stone, and by this means they grind them so fine that many would be puzzled to determine whether they had been turned or ground, were the barrel smoothed lengthways merely to take out the marks of the stone. We have seen the squares of a rifle barrel ground to as perfect an octagon as the eye could assist in forming. Best barrels are generally turned after they are ground. Inferior barrels are struck up with a large rubber, or smooth, by boys; in some instances by women.

There is one advantage derived from grinding barrels, namely, that the friction of the stone being continuous, the temper of the barrel is not so much affected as where the tool in the slide-rest is cutting a considerable portion at once; for all barrels are best, and superior to their compeers, which require least metal to be either ground or turned off their surface, as there is a density on the outer which is not in the interior portion. The harder the material, the less the extent of this objection.

To obtain the true form, it is important that they should be turned. The way of fixing them in the lathe is by having a number of plugs or mandrils, which are perfectly true, and of various sizes, to fit different bores; these are centred and put in the lathe; a carrier is then secured on a part of the plug that projects out of the breech-end of the barrel, and then put into the face-plate of the lathe, which carries it round. The leading screw that travels the slide-rest, is then set in the angle to which the barrel is to be turned (though some lathes have not the power of alteration, but turn all barrels in one angle); the slide is next adjusted to the thickness of the muzzle wanted, and, when all is ready, the lathe is set going; the leading screw is turned at the same moment by the machinery connected, which keeps the tool cutting sufficiently keen to turn a barrel in about twenty-five minutes. This being done, nothing more is required than a fine smooth file to remove the marks of the tool.

There can be no doubt of the superiority of this mode of turning barrels, if due care only be taken with the tool. If it get blunted by any scales or impurities, it is apt to tear pieces out of the barrel, similar to the rings that may be noticed in a slovenly bored barrel, owing to dirt getting on the edges of the bit. In turning a barrel by a common lathe, it is fixed in the same manner as before; about an inch of the surface at the breech and the muzzle is turned to the diameter wanted; the rest is then removed, and half an inch more is turned four or five inches from either end; then another half inch, at another distance of four or five inches, and so on, according to the length; making an allowance each time in the depth of the turning, according to the taper of the barrel. The iron between these cuttings is then filed off by floats the lengthways of the barrel, or more frequently ground off; this is a sure mode of getting the barrels perfectly straight on the outside, and without any of those hollows and shades which may be always discovered in an ill-made barrel. It is astonishing how beautifully many barrels are struck by the float. The mode of turning by the lathe is, however, cheaper, and is now confined to military barrels.

There is a great diversity of opinion as to the proper inclination of a pair of double barrels. It is needless to state the precise distance at which the converging lines drawn from the centre of each barrel, and indicating the inclination of the barrels to each other, should come to a point. If we take the point of convergence of those lines at 2¹⁄₂ yards, it will follow that, at 40 yards, each barrel, were it fixed in a vice, would throw the centre of its charge six inches on the opposite side of the mark fired at; but if the gun be fired from the shoulder, the recoil will invariably cause the gun to swerve outwards, so that at that distance it will never fail to throw the shot in a good direction for the mark or bull’s-eye.