Page:Miscellaneous Papers on Mechanical Subjects.djvu/87

Rh in section by figure C. Either cylindrical of hexagonal bullets may be used. See figures B, b. Supposing a bullet of a cylindrical shape to be fired, when it begins to expand it is driven into the recesses of the hexagon, as shown in figure C. It thus adapts itself to the curves of the spiral, and the inclined sides of the hexagon offering no direct resistance, expansion is easily effected.

It is most important to observe, that with all expanding bullets proper powder must be employed. In many cases this kind of bullet has failed, owing to the use of a slowly-igniting powder, which is desirable for a hard metal projectile, as it causes less strain upon the piece but is unsuitable with a soft metal expanding projectile, for which a quickly-igniting powder is absolutely requisite to insure a complete expansion, which will fill the bore. Unless this is done the gases rush past the bullet, between it and the barrel, the latter becomes foul, the bullet is distorted, and the shooting must be bad. With regard to fouling, it may be prevented by using a proper quantity of lubricating substance, of the right kind and adapted to the temperature of the weather, and a proper charge of powder of the right quality.

If the projectile used be made of the same hexagonal shape externally as the bore of the