the front of the cylinder rather than having to be loaded down the whole length of the barrel. Importantly, this allowed the barrel itself to be rifled, since the user was not required to force the tight-fitting bullet down the barrel in order to load it (a traditional muzzle-loading pistol had a smoothbore and relatively loose-fitting shot, which allowed easy loading, but gave much less accuracy). When firing the next shot, the user would raise his pistol vertically as he cocked the hammer back so as to let the fragments of the burst percussion cap fall out so as to not jam the mechanism. Some of the most popular cap-and-ball revolvers were the Colt Model 1851 "Navy" model, 1860 "Army" model, and Colt Pocket Percussion Revolvers, all of which saw extensive use in the American Civil War. Although American revolvers were the most common, European arms makers were making numerous revolvers by that time as well, many of which found their way into the hands of the American forces. These included the single-action Lefaucheux and LeMat revolvers and the Beaumont–Adams and Tranter revolvers—early double-action weapons in spite of being muzzle-loaders. In 1854, Eugene Lefaucheux introduced the Lefaucheux Model 1854, the first revolver to use self-contained metallic cartridges rather than loose powder, pistol ball, and percussion caps. It is a single-action, pinfire revolver holding six rounds. On November 17, 1856, Daniel B. Wesson and Horace Smith signed an agreement for the exclusive use of the Rollin White Patent at a rate of 25 cents for every revolver. Smith & Wesson began production late in 1857, and enjoyed years of exclusive production of rear-loading cartridge revolvers in America due to their association with Rollin White, who held the patent and vigorously defended it against any perceived infringement by other manufacturers (much as Colt had done with his original patent on the revolver). Although White held the patent, other manufacturers were able to sell firearms using the design, provided they were willing to pay royalties. After White's patent expired in April 1869, a third extension was refused. Other gun-makers were then allowed to produce their own weapons using the rear-loading method, without having to pay a royalty on each gun sold. Early guns were often conversions of earlier cap-and-ball revolvers, modified to accept metallic cartridges loaded from the rear, but later models, such as the Colt Model 1872 "open top" and the Smith