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

It had long been known that to give a spiral motion to a bullet in a direction coincident to its line of flight, was the standard of perfection in rifle projectiles; but this, until the invention of the expansive bullet, could never be attained with safety.

Spheres receiving this motion are not likely to retain it, because the periphery of the spherical bullet is, in all cases, subjected to much more friction than the rest of the sphere; a change would therefore certainly be induced, the axis of the spinning motion being changed from one coincident to the line of flight to that of one vertical to the same. The two grooved rifle was an illustration of this; for in all cases the projections on the bullet induced a change, the ring of the bullet revolving parallel to the horizontal line, as I predicted in 1841.

Enough has been said to point out the prejudicial action of any projections on projectiles, both as regards their accuracy and length of flight; perfect smoothness of surface being, in fact, absolutely necessary. Lengthened study and a series of experiments with bullets of a sphero-cylindrical shape having grooves and projections on their exterior identical with the grooving of the interior of the barrel, led me to consider the production of a bullet with a considerable cavity (equal, in fact, to two-thirds of its length) at the same time adopting as a standard one and a half diameters in the length of the bore of the gun; thus the thickness of the metal between the apex of the bullet and apex of the cavity was nearly one half of the diameter, as the following diagram will show.

This enabled me to insure two important principles, on which depended the success of the whole invention. 1st. The centre of gravity was in the head of the projectile. 2nd. “The force was communicated directly to the centre of gravity during the explosion.” This is a most important principle, which all writers presuming to give their version to the theory of the expansive system, have entirely overlooked.

If the arrow could receive the propelling force in the head, its motion would be even, and free from “hobbling,” as Roger Ascham wishes it to be; but if, on the contrary, it is received at the opposite extremity, then there is a struggle between the head and the tail, as to which shall be first, and a “wobbling” motion is induced, enduring until an equilibrium of velocity is established.

It is essential to all future progress in the science of projectiles, that this point should be remembered, and its importance duly estimated; and it is possible to apply this principle to projectiles of any weight. If this point be attended to, where is the difficulty in extending the length of our projectiles to that of arrows? thus increasing their range indefinitely. There is, in fact, no law to limit the length of expansive bullets: the only limit to their length now is the tendency of lead to squash; but alloys of lead and other metals may yet be beneficially used for projectiles, and that to an extent of which at present we can form no conception.

The range of vision of the human eye being inferior to the range of the rifle will probably be the only limit to its use; and this range will not be difficult to attain: reduction in the size of bore enables us to elongate the bullet without diminishing its weight or the accuracy of its range; but without the existence of a cavity to insure the force being applied to the head of the bullet, this cannot possibly be done; whilst all other shapes are limited in their application, and an extension of range cannot be obtained with them.

Next to these two important points in the invention comes the question of expansion, whereby the grooves of the rifle are filled up with lead, and windage is as far as possible obviated. The expander I first employed consisted of a tapering piece of iron, similar in shape to the frustum of a cone, and this, when inserted into the cavity of the bullet, was flush with the bottom of the cylinder. The force generated by the ignition of the charge was exerted equally on the plug and on the leaden cylinder; the plug, however, moving more rapidly than the lead, is driven quicker into the bullet, the bullet expands, and thus the filling up of the grooves is accomplished. There can be no doubt that at the same time an upward force is exerted by the plug on the leaden bullet; and that, too, of a more elastic character than would be exerted by the gases themselves, if they were allowed to act directly with all their force upon the lead; for it is a fact beyond all dispute, that any force tending to set matter in motion gradually is more effective than that which is instantaneous in its action.