A BALL-BEARING RIFLE
Rapidity of fire is only one of the desirable features in a firearm. Its range—or perhaps we had better say its muzzle velocity—is of almost equal importance. The greater this is, the flatter is the trajectory or curve described by the bullet, and the more extended the "point blank" range and the "danger zone."
Take the case of two rifles capable of flinging a bullet one mile and two miles respectively. Riflemen seldom fire at objects further off than, say, 1,200 yards; so that you might think that, given correct sighting in the weapon and a positive knowledge of the range, both rifles would have equal chances of making a hit.
This is not the fact, however, for the more powerful rifle sends its bullet on a course much more nearly parallel to the ground than does the other. Therefore an object six feet high would evidently run greater risks of being hit somewhere by the two-mile rifle than by the one-mile. Thus, if at 1,200 yards the bullet had fallen to within six feet of the ground, it might not actually strike earth till it had travelled 1,400 yards; whereas with a lesser velocity and higher curve, the point of impact might be only fifty yards behind. Evidently a six-foot man would be in danger anywhere in a belt 200 yards broad were the high-velocity rifle in operation, though the danger zone with the other weapon would be contracted to fifty yards.
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.
The following misprints and misspellings are noted or have been corrected in the text
Page 38: Superscript "1" changed to an inline fraction "1/8" in "50,000 prick-marks 1/8 inch apart".
Page 55: "corp" changed to "corps" in "a corps of inventors".
Page 145: "populsion" changed to "propulsion" in "for its own propulsion".
Page 173: "searchlight" changed to "search-light" in "when a search-light alone", to make the latter usage consistent throughout the book.
Page 206: "two" changed to "too" in "the reversal being too sudden".
Page 244: According to the 1911 Encyclopædia Britannica, "Kleingert" is the correct spelling of the name of the German who invented the "first practical diving helmet". More modern books, however, use a different spelling, referring to (Karl Heinrich) Klingert.
Page 250: "Saint Goubin" changed to "Saint Gobain" in "by Saint Gobain, of Paris".
Page 266: "overburden" changed to "over-burden" in 'removing the "over-burden" of surface mines' to make the latter usage consistent throughout the book.
Other changes to the text
Footnotes have been relabeled using numbers then collected together at the end of the chapter in which they appear. This has the consequence that, where the same reference is cited in more than one footnote in a chapter, it can result in a sequence of footnotes with identical text. That is not a transcription error.