The Percussion Cap.

SUBJECT: The Percussion Cap.

The invention of the percussion lock is often credited Alexander Forsyth, a Scottish clergyman, which patented a percussion lock in 1805 (some claim 1807 – unproven). The percussion lock had a hammer rather than a cock. A fulminating copper cap was placed on a hollow nipple, also called the piston. The nipple had a flash channel that lead into the main charge. When the hammer was released it hit the cap which ignited the cap which in turn ignited the powder. The percussion lock was a major improvement compared to the flintlock. Now shooting in bad weather wasn't a problem, flames and sparks in the shooters face was eliminated and the ignition time was considerably shorter. The percussion era did not last long, and already in the 1860s the metallic cartridge started to gain a foothold.

Gunsmiths like Joseph Maton invented more reliable forms of ignition, like the tube lock in 1814. The artist Joshua Shaw designed what is recognized today as the percussion cap, which he patented in the United States in 1822, since Forsyth had threatened his rivals in Britain with legal action. These new forms of ignition proved popular among hunters during the Regency Period, who had their old reliable flintlocks converted to the new system.

Forsyth recorded his invention with the Tower of London, byname the Tower, royal fortress and London landmark. Its buildings and grounds served historically as a royal palace, a political prison, a place of execution, an arsenal, a royal mint, a menagerie, and a public records office. This was why he placed his patent here for public record and secure from others. It is located on the north bank of the River Thames, in the extreme western portion of the borough of Tower Hamlets, on the border with the central City of London.

William Hovey Smith wrote:
Compared with the matchlock, wheellock and flintlock systems that preceded it, the concept of firing a gun using a pill, tube, tape or cap containing a percussion compound would seem to be quite simple. You just put the percussion device on the gun, and pull the trigger — right?

This is true as far as it goes, but despite the system’s simplicity, thousands of game animals are missed each year because percussion guns failed to fire. The percussion system appears so obvious that most hunters do not give it the attention that it deserves.

The elegant, but delicate pill locks and tube locks are long gone. Tape primers used on some Civil War Muskets and Sharps’ rifles are presently regaled to cap pistols. What remains for modern black-powder shooters are percussion caps in several varieties and sizes, 209 shotgun primers used on a number of in-line (and a few sidelocks) rifles and shotguns, and adapter systems to use small rifle primers such as for the Markesbery rifles and shotguns.

Percussion Caps

All modern percussion caps are made of copper with a dab or wafer of percussion compound glued to the inside top of the cap. Caps made by Remington and CCI and are produced in the U.S., and others imported from England, Germany and Italy are also found in the United States. The most commonly used sizes are No. 10s for percussion revolvers and small pistols and No. 11s for many percussion rifles and single-shot pistols. Older replica rifles, outside of military long arms, take the No. 11 caps. Muskets, Sharps rifles and Civil War carbines use the larger top-hat musket caps, which may come with or without flanges on the bases.

Typical problems with caps are as follows: They lose their percussion compounds before being put on the gun’s nipples, and will not fire. The caps fit too loosely and fall off the nipples leaving the nimrod snapping his empty gun at a deer. The caps fit so loosely on the nipples that it takes one fall of the hammer to seat the cap and another to fire the gun. Also, moisture can wick up the sides of the caps and spoil the percussion compound, or rain wets the caps as they are put on the gun. Another potential problem is the detonation of the percussion cap blows metal fragments into the mechanism and prevents a revolver’s cylinder from turning or hammer to fall. Or, a cap is fired on an empty rifle to dry out the gun and a piece of foil or paper clogs the nipple.

Nipples have their own series of ills that may prevent a cap from functioning. These include being battered at the top, or breaking so the cap does not fit the nipple. Nipples are clogged by firing residue and do not allow the flame to enter the barrel. The top of the nipple can be chipped or worn preventing the hammer from striking the nipple squarely and firing the gun. The nipple can be cross-threaded and may be blown from the gun, possibly injuring the shooter or a bystander. Another problem can rise if several guns have been cleaned at once and the wrong-threaded or size nipple is installed on a gun.

Hammer sometimes have problems, too. They may not strike the nipple squarely, resulting in unreliable ignition. Other problems include: the hammer may be too small to be used on a gun, particularly when a gun is converted from a No. 11 cap to a musket cap. Or the inside of the hammer can be mis-aligned from repeated impact and not hit the cap squarely. Or the hammer may simply break.