Many theories have been advanced, and many conjectures made as to the cause of the recoil of guns; and it must be evident that the causes vary with the form of gun, with the nature of the gunpowder, and the weight; or peculiar arrangement of the shot or bullet. For instance, an ounce of shot, and an ounce of lead in the form of a round bullet, fired from the same gun would give two very different amounts of recoil, when measured by the spring cushion; the ounce bullet not giving much more than half the recoil produced by the ounce of shot. This is owing to the simple fact that the bullet being a compact body, offers only the resistance of its weight, and the simple friction of sliding or rolling along the barrel according as it is tight or loose; but the tendency of the hundreds of shot corns is to “jam and wedge” in the most extreme manner, offering, by their lateral pressure against the sides of the barrel, the greatest amount of friction and reluctance to be driven out: hence the reaction on the gun, and thence on the shoulder of the shooter; and the smaller the size of shot the greater the jamming. Again, the same weight of shot, fired from a 16-bore and a 12-bore will recoil much more in the smaller than in the larger bore, even when all other points are equal; because the charge reaches higher in the 16-bore, thus offering at first a greater amount of inertia. Secondly, there is also more tendency to jam; and, thirdly, the extension of the surface of lateral pressure on the tubes of the barrel must also add to recoil. Dirty guns, it is well known, kick violently, simply from the greater friction, or difficulty of the matter of the charge being put in motion.