Various experimental breech loaders had been in existence since the 16th century, however developments such as the Ferguson rifle in the 1770s and early pinfire cartridges in the 1830s had little impact on sporting rifles due to their experimental nature, expense and the extraordinary strength and reliability of the percussion muzzleloader. In 1858, Westley Richards patented the break open, top leaver breech loading action, whilst a useful development these early break open designs had a great deal of elasticity in the action and upon firing they sprung open slightly, a problem that gradually worsened with repeated firing and with more powerful cartridges. Many gunmakers tried various methods to rectify this problem, all to little avail until Westley Richards invented the "Dolls head" lock in 1862 which greatly improved rigidity, this was followed by James Purdey's under-locking mechanism in 1863 and W.W. Greener's "Wedge fast" system in 1873, finally the basic break open action known to this day had the strength required to meet the stresses of large-bore projectiles. By 1914, triple, quadruple and even quintuple locking designs could be found in various proprietary actions.