The next improvement was to eliminate the match, replacing it with a method that could generate fire on demand. Adapting household fire-starting implements, such as flint and steel, was the obvious choice. A flint creates a spark under conditions that would extinguish a match.
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The first flint-fired arms were wheel locks from the early sixteenth century. History credits the wheel lock to Germany and/or Austria. A steel wheel with a serrated or knurled outer edge projected through the lock plate (the mounting plate for the ignition parts). The wheel was attached internally to a spiral spring and could be wound like a clock, storing energy in the wheel. A cock gripped a piece of flint (or iron pyrite) and could be lowered onto the wheel. Pulling the trigger momentarily released the wheel and lowered the flint on the spinning wheel, producing sparks. The sparks fell into a small pan containing a few grains of powder. A small hole, the vent, connected the exterior pan to the main powder charge in the barrel. When the powder in the pan fired, some of the fire traveled down the vent and initiated the main charge. The lighting mechanism of a modern cigarette lighter has corresponding parts; the wheel is turned manually and the lighter uses a fuel-soaked wick or butane jet in place of a powder pan.
The wheel lock proved to be significantly more reliable than the cannon lock and the matchlock. However, this progress incurred considerable financial cost. The locks were crafted by highly skilled artisans and required a level of precision not typically associated with manufacturing techniques of this historical period.
To reduce a firearm’s trigger pull when the wheel was fully tensioned, the set trigger was developed using a spring-driven lever linkage. Today, the set trigger is used in precision target arms where a minimum trigger pull is mandatory.
The wheel lock was unsuitable for use in combat due to the following factors:
- Too expensive for arming a large force of soldiers
- Too complex to be relied upon in combat
- Exposure to dirt and firing residues made fine-fitting parts nonfunctional
- Loss of the spanner wrench for winding the spring rendered the gun inoperable
Ultimately, the wheel lock was associated more with social status than as a military arm. It was the arm of choice for the rich nobleman who wished to impress his peers.
In spite of its problems, the wheel lock inspired future development that overcame cost and complexity issues and continued the improvement of firearms.