At close quarters a flat trajectory is even more valuable, since it diminishes the need for altering the sights. If a rifle's point-blank range is up to 600 yards, you can fire at a man's head anywhere within that distance with a good chance of hitting him. The farther he is away, the lower he will be hit. A high trajectory would necessitate an alteration of the sights for every fifty yards beyond, say, two hundred.
The velocity of a projectile is increased—(1) by increasing the weight of the driving charge; (2) by decreasing the friction between the barrel and the projectile.
An American inventor, Mr. Orlan C. Cullen, has adopted a means already well tried in mechanical engineering to decrease friction.
He has produced a rifle, the barrel of which has in its walls eight spiral grooves of almost circular section, a small arc of the circle being cut away so as to put the groove in continuous communication with the bore of the barrel. These grooves are filled with steel balls, one-tenth of an inch in diameter, which are a good fit, and on the slot side of the groove project a very tiny distance into the barrel. The bullet—of hard steel—as it is driven through the barrel does not come into contact with the walls, but runs over the balls, which grip it with sufficient force to give it a spinning motion. The inventor claims that there is no appreciable escape of gas round the bullet, as the space between it and the barrel is so minute.
The ball races, or grooves, extend back to the powder chamber and forward to the muzzle. Their twist ceases a short distance from the muzzle to permit the insertion of recoil cushions, which break the forces of the balls as they are dragged forward by the bullet.
Mr. Cullen holds that a rifle built on this principle gives 40 per cent. greater velocity than one with fixed rifling—to be exact, has a point-blank range of 650 yards as compared with 480 yards of the Lee-Metford, and will penetrate 116 planks 1 inch thick each.
The absence of friction brings absence of heat, which in the case of machine-guns has always proved a difficulty. It also minimises the recoil, and reduces the weight of mountings for large guns.
Whether these advantages sufficiently outweigh the disadvantages of complication and cleaning difficulties to render the weapon acceptable to military authorities remains to be seen. We can only say that, if the ball bearing proves as valuable in ballistics as it has in machinery, then its adoption for firearms can be only a matter of time.
PLYMOUTH: W. BRENDON AND SON, LTD., PRINTERS.