RECOIL

, or Rebound, the resilition, or flying backward, of a body, especially a fire-arm. This is the motion by which, upon explosion, it starts or flies backwards; and the cause of it is the resistance of the ball and the impelling force of the powder, which acts equally on the gun and on the ball. It has been commonly said by authors, that the momentum of the ball is equal to that of the gun with its carriage together; but this is a mistake; for the latter momentum is nearly equal to that of the ball and half the weight of the powder together, moving with the velocity of the ball. So that, if the gun, and the ball with half the powder, were of equal weight, the piece would recoil with the same velocity as the ball is discharged. But the heavier any body is, the less will its velocity be, to have the same momentum, or force; and therefore so many times as the cannon and carriage is heavier than the ball and half the powder, just as many times will the velocity of the ball be greater than that of the gun; and in the same ratio nearly is the length of the barrel before the charge, to the quantity the gun Recoils in the time the ball is passing along the bore of the gun. So, if a 24 pounder of 10 feet long be 6400lb weight, and charged with 6lb of powder; then, when the ball quits the piece, the gun will have Recoiled (28/6400) X 10 = 7/160 of a foot, or nearly half an inch.