The Whitworth rifle was designed by Joseph Whitworth, who was an English engineer in response to a request by the British Board of Ordnance for a universal troop rifle. The original design was a small-bore .45 caliber hexagonal-barreled rifle which fired a 530gr. six-sided bullet. Rifles were built for the 1858 trials, where the Whitworth competed against the existing .577 Pattern 1853 Enfield. Both rifles performed equally well up to 500yds, but beyond that, the Whitworth rifle outperformed the Enfield by a wide margin. The increasing popularity of breech-loading rifles, fouling from black powder residue, together with the expense of building the Whitworth meant that there was little chance that it would gain any government orders. After further tests, it was found that the conical bullets provided accuracy that was on par with the original hexagonal bullets and the two designs were used together. The Whitworth was used to an extent by the Confederate Armies during the American Civil War.

Source: www.americanrifleman.org