Notes about the history of engineering

[greyofk]

Evolution of the cartridge

The good muzzleloader of 1850^th had better reliability than Glock or Kalashnikov. Percussion cap always worked and there were no failures to feed or eject. However better rate of fire brought breechloaders to the armies of all European countries.

Mid XIX century witnessed many different version of cartridges. They were made of steel, brass and paper in every possible combination. A primer could be located on the bullet, at the button or even on the wall of a cartridge. The most common feature of early cartridges was low reliability. A primer integrated into early cartridges was subject to misfire. An army company with 30 cartridge fed rifles was superior to a company with 30 muzzleloaders. However as an individual weapon breachloader did not match expectations. For this reason majority of revolvers of that time were of “cap and ball†design. They were slow to load, but they shot for granted.

What was wrong with primers? A primer reliably ignites when it is smashed between hummer and anvil. In case of percussion cap the nipple served as an anvil and the hummer served as a hummer. Early cartridges did not have stable anvil. Advanced armorers of mid XIX come with idea of rimmed metal case. The outside diameter of a case was smaller than inside diameter of a chamber for easy loading. The base of the shell had a rim with the diameter greater than chamber. The rim prevents the shell from “sinking†into the chamber. How to prevent hot gases from streaming in cartridge to chamber gap? It was absolutely necessary for 2 reasons. Leaking gas means lost of the pressure in the chamber and loss of the muzzle energy. More important such streaming gas is directed toward the face of a shooter. Preventing the gas leakage called obturation. The obturation was achieved by expansive shell.

First efficient expansive shell was made from brass by the French gunsmith Casimir Lefaucheux in 1836. However his pinfire ignition system was far from perfect. His shell had never seen mass production. The key point of his invention was thin brass cylinder. The brass is somewhat unique. The brass shell expands from the force of burning gunpowder . It perfectly fits the chamber and forms an efficient gas check. After the shot the brass shrinks a little bit. This “little bit†is enough to extract the spent shell from the chamber.

The other bright idea belong to French engineer Flobert. He managed to make a shell with double walled rim by rolling stamped metal caps. He placed priming compound in the rim. The priming compound could be ignited bu smashing the rim. There is common belief that British William Eley invented rimfire ammunition. Some even call rimfire primer “ Eley primerâ€. William Eley established an ammunition company that later produced the best rimfire ammunition, but he did not invent this cartridge. Flobert obtained his pattern as early as 1831, however his cartridge missed the main part. It had no gunpowder. By 1845, this had evolved into the Flobert .22 BB cap. The .22 BB cap was essentially just a percussion cap with a round ball pressed in the front, and a rim to hold it securely in the chamber. Intended for use in an indoor "gallery" target rifle, it relied entirely on the priming compound for propulsion. Velocities were very low, the cartridge was ignored by military. However it was the grandfather of all rimfire cartridges. The next rimfire cartridge was the .22 Short, developed for Smith and Wesson's first revolver, in 1857; it used a longer rimfire case and 260 mg of black powder to fire a conical bullet.

A rimfire cartridges are cheap in production and relatively reliable. They were a popular solution for revolvers and early rifles. They can only be used for low powered cartridges. The case has to be soft enough to be deformed by the firing pin, which detonates the priming compound in the rim. It means thin metal on the base of the cartridge. The thin metal can not withstand any significant pressure. In the past, rimfire cartridges from 2.34 mm to .58†were in production. The trend of XIX century was transition to small bore, short barrel and high pressure. The high pressure killed most of rimfire calibers. Only .22 and .17 survived nowadays. The .22 Long Rifle is still the most common cartridge in the world.

To be continued