Page:Miscellaneous Papers on Mechanical Subjects.djvu/92

 in the hexagonal system, rifling may be effected independently of expansion, by making the projectile of the same shape as the interior of the barrel: in other words, by having a mechanical fit between them. The projectile may be used naked, and be made of metal of any degree of hardness. The expansion principle may also be combined with an easy mechanical fit, so that a projectile of metal harder than lead, as an alloy of lead and tin, may be used, which, while it loads easily, will expand sufficiently to fill up the bore, and give more than double the penetration of lead.

This system thus admits of the employment of projectiles of different densities and varied shapes, suitable for special purposes. If for example it be required to fire through plates of iron, a flat-fronted projectile of steel of the form shown in figure E, will be employed. When the flat-fronted projectiles were fired in comparison with those having rounded fronts, like figure B, from the same barrel, and under precisely similar conditions as to range (500 yards), charge, and weight, the pointed projectiles were not found to possess any great practical advantages over the flat ones, for the elevation of the former was only a minute and a-half better than that of the latter.

It was satisfactory to find that so slight a