Purdey guns moved briskly from flintlock to percussion cap to hammer centre-fire guns and then to the self-opening hammerless gun of 1880. This hammerless self opening mechanism was designed by Frederick Beesley, a Purdey worker of the time, and used one limb of a V spring to operate the internal hammers and the other to operate the self opening feature. Beesley sold the patent to Purdey in 1880 for £55. This was followed ten years later by the incorporation of ejectors. Apart from continual refinement and the optional single trigger mechanism, very little change has subsequently been made to the design of the side-by-side gun.