A barrel, which recoils from being light, or from not being held firmly when fired, throws shot very weakly. So, on the other hand, barrels which have sufficient weight to break the recoil, or which are placed against something solid when fired, have their shooting power amazingly increased. The reason is, that when the gun is allowed to recoil, a portion of that power which should be employed in expelling the shot is uselessly expended on a yielding surface in a contrary direction: whereas, when the barrel is firmly fixed, or is of sufficient weight to break the recoil, that portion of the explosive force which strikes against the breech rebounds and is forced back upon the shot, and consequently becomes a portion of the available strength of the charge. This explains why the weight of the gun rather than a difference in length or bore regulates the shooting power. In what follows, Mr. Greener,[3] whose book contains a lucid exposition of the nature of projectile force, shows this more clearly:—
“The fact that the shooting powers of a gun are increased by its being fixed in an immoveable frame, is proved with the practice of mortars. Mortars on iron beds, and these firmly embedded in the earth, will throw a shell farther when on the ground than when placed on a platform, or on board a ship. It is for the purpose of destroying the recoil, that mortars for sea service, though of the same calibre as those intended for land-service, are made three times the weight. Dr. Hutton states, that he found no advantage by retarding the recoil in practice with artillery. He means, that no advantage is gained by stopping at three feet a gun accustomed to recoil to the distance of six. The statement is perfectly true. If he were to allow a gun to recoil only an inch, and then to strike against a solid substance, he would gain nothing. For if it recoil ever so little, the shooting force is as much weakened as if it recoiled twice as far.
“To increase that force, a steady fixed resistance is required. The velocity of the projectile depends on the force of the immediate impulse. Before a gun, suffered to recoil, could rebound from striking some solid substance in its recoil, the charge would be gone, and could, therefore, receive no additional impetus from that rebound. The truth of this fact may be illustrated by throwing a hand-ball against any loose body with sufficient force to displace it. However hard or elastic that body might be, the ball would not rebound from it, but would fall perpendicularly down. Fix and secure that same body, and then the ball will rebound with little less force than that with which it was thrown against it. So it is with gunpowder. If it meet with a firm resistance, it will rebound and project the ball or shot with additional force.”