Many early firearms, while representing a considerable advance over earlier weapons, possessed an inherent liability with the extended time necessary for their reloading after firing a single shot. Perhaps the earliest reliable ignition system employed with these single-shot arms was the wheel lock. This early German "Dag," as early wheel lock pistols were sometimes called, had a bore slightly over a half-inch in diameter and could have fired either a single projectile or a load of smaller shot against adversaries. As part of the loading process for this muzzleloading pistol, a special wrench was needed to wind the wheel lock's innovative circular spring.
The invention of the wheel lock ignition system itself has been attributed to Leonardo da Vinci. A helical spring mechanism is shown in his Codex Atlanticus (c.1500) manuscript and several dated wheel lock rifles and pistols based on this principle are known from the 1530s. The spring-driven serrated wheel, when brought into contact with a piece of iron pyrite or flint in the jaws of the hammer, produced sparks to ignite the priming in an exterior pan. While either flint or pyrite could be employed in wheel lock arms, early armorers selected rounded profile flints and pyrites to mitigate chipping or damage to the serrated wheel.
No doubt once owned by a wealthy individual and elaborately adorned with numerous inlays of bone and ivory, the pistol also had an impressive ball-shaped butt. While providing excellent balance for the heavy barrel, the ball butt feature also allowed the pistol to be quickly wielded as a convenient club if necessary. Early cavalry forces armed with similar dags practiced a close combat drill where mounted troopers discharged their barrels, reversed their pistols and swung them against padded targets.