The reason that the two barrels of a shot gun or rifle will, if put together parallel, throw their charges in diverging lines has never yet been satisfactorily accounted for, although many plausible and ingenious theories have been advanced for the purpose.  The natural supposition would be that this divergence resulted from the axes of the barrels not being in the same vertical plane as the center line of the stock.  That this is not the true explanation of the fact, the following experiment would tend to prove.

[Illustration:  EXPERIMENTS WITH DOUBLE-BARRELLED GUNS.]

Fig. 1 represents a single barrel fitted with sights and firmly attached to a heavy block of beech.  This was placed on an ordinary rifle rest, being fastened thereto by a pin at the corner, A, the block and barrel being free to revolve upon the pin as a center.  Several shots were fired both with the pin in position and with it removed, the barrel being carefully pointed at the target each time.  No practical difference in the accuracy of fire was discernible under either condition.  When the pin was holding the corner of the block, the recoil caused the barrel to move from right to left in a circular path; but when the pin was removed, so that the block was not attached to the rest in any way, the recoil took place in a line with the axis of the bore.  It will be observed that the conditions which are present when a double barreled gun is fired in the ordinary way from the shoulder were in some respects much exaggerated in the apparatus, for the pin was a distance of 3 in. laterally from the axis of the barrel, whereas the center of resistance of the stock of a gun against the shoulder would ordinarily be about one-sixth of this distance from the axis of the barrel.  This experiment would apparently tend to prove that the recoil does not appreciably affect the path of the projectile, as it would seem that the latter must clear the muzzle before any considerable movement of the barrel takes place.

With a view to obtain a further confirmation of the result of this experiment, it was repeated in a different form by a number of shots being fired from a “cross-eyed” rifle,[1] in which the sights were fixed in the center of the rib.  Very accurate shooting was obtained with this arm.

   [Footnote 1:  A cross-eyed rifle is one made with a crooked stock
   for the purpose of shooting from the right shoulder, aim being
   taken with the left eye.]

A second theory, often broached, in order to account for the divergence of the charge, is that the barrel which is not being fired, by its vis inertia in some way causes the shot to diverge.  In order to test this, Mr. Phillips took a single rifle and secured it near the muzzle to a heavy block of metal, when the accuracy of the shooting was in no way impaired.