7. T. L. Davis, Chemistry of Powder and Explosives, 3rd ed. (London: Chapman & Hall), 39.
8. W. W. Greener, The Gun and Its Development, 9th ed. (London: Arms and Armour Press), 13.
9. William Chipchase Dowell, The Webley Story (Leeds, UK: Skyrac Press), 179. 10. Davis, Chemistry of Powder and Explosives, 39.
History of Ignition systems
Ignition of the propellant was a major problem from the introduction of gunpowder in the early fourteenth century until the development of a percussion primer by a Scottish clergyman, the Reverend Alexander John Forsyth,
The first means of igniting the propellant was by placing a glowing twig or a hot wire into a touch hole at the rear of the barrel where it came into contact with the propellant. This direct method of ignition had many disadvantages: the firer needed to be near a fire, ignition was at the mercy of the wind and the rain, and it was difficult to aim properly.
To overcome the lack of mobility the "slow" match was developed. The match consisted of a piece of cord which had been soaked in a strong solution of potassium nitrate and then dried. When placed in the touch hole and lit, the match would smolder with a glowing end at the rate of about an inch a minute until it reached and ignited the propellant.12 Speed of ignition and dependence on weather conditions were serious disadvantages.
The first mechanical device to achieve ignition was the matchlock which derived its name from the "slow" match. The match was attached to the gun by a match holder and the action of the trigger lowered the glowing end of the match into a flash pan which contained loose gunpowder (priming powder). The powder in the pan was ignited (flashed) by the glowing match end and the flame was passed through a small barrel vent to ignite the main pro-pellant charge. This was a major improvement in ignition systems as the time of discharge closely coincided with the pull of a trigger. Early matchlocks had an open flash pan and consequently a sudden gust of wind could remove the gunpowder from the flash pan. This was partly solved by fitting a cover over the flash pan, although the smoldering match system of ignition was still dependent on weather conditions.
The next major improvement in ignition systems was the wheellock. It worked in the same way as the matchlock by conveying the flame from the gunpowder in the flash pan through a barrel vent to ignite the main pro-pellant charge. However, the ignition of the powder in the flash pan was achieved by sparks from flint stones or pyrites being held by a moving arm drawn down against a spring-operated, spinning serrated metal wheel.13 The spring for the wheel had to be tensioned with a key before firing each shot.
A more reliable and important variation of the principle of the wheellock was the flintlock. In the wheellock sparks were produced by a grinding motion whereas in the flintlock system sparks were produced by a striking motion.
A cock or hammer with a piece of beveled flint securely clamped to it and an L-shaped steel flash pan cover, called a frizzen, completed the spark making battery. When the hammer fell, the flint struck the upper face of the hinged pan cover (forcing it open and exposing the gunpowder in the pan) and caused sparks which ignited the gunpowder in the pan. Again, the flame from the gunpowder in the pan was directed through a small vent in the barrel causing the main propellant charge to ignite.14
All the means of ignition, from the hot wire to the flintlock, were dependent to a greater or lesser extent on the weather conditions and none offered the reliability of ignition experienced with modern ammunition. However, the flintlock was a very efficient mechanism, and with the introduction of a waterproof flash pan in 1780,15 the flintlock offered the shooter a reasonably reliable means of ignition under most weather conditions.
The flintlock was not without its faults. Misfires were not uncommon and since each piece of flint was serviceable for only 20 to 30 shots, the ignition system had to be efficiently maintained. The priming powder remained a potential weakness since wind or rain could dispose of it at the crucial moment of firing. Also the small time delay between pulling the trigger and the ignition of the main propellant charge was annoying. It took time for the flint to scrape along the frizzen and for the sparks to fall into and ignite the main propellant charge. The shooter had to make allowance for the delay especially when aiming at moving targets. A quicker and more reliable means of igniting the main propellant charge was needed.16
According to many writers, the Reverend Alexander Forsyth studied a group of chemical compounds called metallic fulminates whose existence had been known from 1800. It was also known that they exploded with a flash when struck a sharp blow with a hard object. In 1805, he applied this property of metallic fulminates to firearms ignition, thereby inventing the percussion system of ignition.
In 1807 he took out a patent on his invention by which a pivoted magazine deposited a few grains at a time of mercury fulminate into a touch hole in the barrel of the firearm. The mercury fulminate was detonated by a blow from the hammer of the firearm sending flame through the touch hole to ignite the propellant. "Instant" ignition had been achieved.
The pivoted magazine was too complicated and subsequent development by other workers was geared toward a more convenient and efficient means of presenting the mercury fulminate to the firearm.
This led to several short-lived innovations including the tubelock, patch-primers, and the pill-lock eventually leading to the percussion cap, which proved to be the most efficient and practical way to package the primer. The development of the percussion cap (small waterproof copper cups) is credited to Joshua Shaw in 1816.17 The cap (primer) was placed over a permanent hollow nipple, screwed into a flash hole in the gun barrel, and detonated by the crushing impact of the hammer.
Was this article helpful?