Page:Miscellaneous Papers on Mechanical Subjects.djvu/89

Rh of powder they penetrated through 7 inches of elm planks.

At first I was desirous of using, if possible, the turn adopted for the Enfield Rifle, for firing long projectiles, and I tried various shapes and combinations of metal, so as to place the centre of gravity in different positions more or less forward; but when they were fired, the marks left by their passage through a paper screen, placed about 6 feet from the muzzle of the rifle, showed that they all turned over within that distance, because the rotation given by that comparatively slow turn invariably proved insufficient to keep them point foremost. For an ordinary military barrel, 39 inches long, I proposed a .45-inch bore, with one turn in 20 inches, which is, in my opinion, the best for this length. The rotation is sufficient, with a bullet of the requisite specific gravity, for a range of 2,000 yards. The gun responds to every increase of charge, by giving better elevation, from the service charge of 70 grains up to 120 grains; this latter charge is the largest that can be effectively consumed, and the recoil then becomes more than the shoulder can conveniently bear with the weight of the service musket.

The advocates of the slow turn of one in 6 feet 6 inches consider that a quick turn causes