My article about Joseph Whitworth and his rifles is up on the Shock Troops web site. It originally appeared in the December 2010 issue of Civil War Times.
In 1854, at the request of the British Board of Ordnance, Whitworth turned his attention to firearms, specifically the Enfield P53 .577 caliber service rifle, which he found “wrong in every particular. The diameter of the bullet was too large for the size of the gun, the bullet itself was too short, and the twist of rifling was not one-third of what it should have been.”
Accordingly Whitworth began work on an improved rifle, his only restrictions being to keep the same weight as a service bullet—530 grains—and the standard 70 grain powder charge. His first step was to build an enclosed 16×20’gallery 500 yards long with a series of light paper screens to record the trajectory of the bullet. After much experimentation he reduced the caliber to .45, which allowed him to stretch the projectile to three times as long as its diameter. He also gave the bore an extremely fast twist—one turn in 20 inches as opposed to one in 78 inches for the Enfield. His rifle also featured an unorthodox bore configuration—a six-sided hexagonal spiral rather than the conventional arrangement of lands and grooves.
This also allowed Whitworth to use a bullet fitted to the bore rather than relying on the Minie principle, in which the base of a soft lead bullet expanded when fired to grip the rifling. As he put it: “It is perfectly easy to form a mechanically-fitting bullet adapted to the hexagonal rifling, on account of the simplicity of the form, but quite impracticable to obtain an accurate fit between the bullet and the bore of the rifle where any system of grooves is adopted.”
Since the bullet did not need to expand it could be made of a harder and denser material such as an alloy of tin and lead or even of steel, giving it markedly increased penetrative power. The hex-bore design also caused less friction, allowing a considerably higher muzzle velocity (13-1400 fps vs. 850-900 fps). He also discovered that a bullet’s long range performance could be improved by tapering the rear end, a feature later called the “boattail.”
Field trials in 1859 showed the Whitworth to be overwhelming superior to the Enfield, especially at long ranges. The Whitworth’s “figure of merit” (a measure of the average hit dispersion) was slightly better at 1400 yards than was the Enfield at 500. In penetration tests, the hard alloy bullet passed through 34 half-inch elm planks while the Enfield penetrated only 12. Nevertheless the ordnance board rejected his rifle on the dubious grounds that the .45 caliber bore was too small for military use (ironically, ten years later a similar board would conclude that this caliber was optimal for a service rifle). This ignited a long-running feud between Joseph Whitworth and the Ordnance boffins.
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