Sunday, May 2, 2010

Cartridges: Needle Gun Cartridge

As we've seen in our previous discussion about paper cartridges, these were mainly used with muzzle-loader weapons. We've also studied percussion lock mechanisms, where ignition of the gunpowder is achieved by using a percussion sensitive primer (e.g. mercury fulminate or potassium chlorate) to set off the main gunpowder charge. Instead of using a separate percussion cap to do this, the next logical development in cartridge technology was to include the percussion cap as part of the cartridge. This way, the user can quickly reload the weapon simply by opening the weapon at the breech end, dropping in a new cartridge and then closing the breech and cocking the weapon. These cartridges were also instrumental in making breech-loader weapons start to replace the older muzzle-loader weapons.

The Prussian Dreyse Needle gun followed by the French Chassepot rifle were among the first mass-produced military weapons that used breech-loader technology. The cartridge that went with them was still made of paper at this point, but it had some interesting features:

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It consists of a paper cartridge that contains an oval shaped bullet glued to one end. The other end is filled with a charge of black powder. Towards the middle is a percussion cap C, which contains a shock-sensitive primer (potassium chlorate or mercury fulminate). When the weapon is fired, a sharp needle held by a spring is forced into the cartridge and makes its way through the gunpowder until it contacts the percussion cap. Due to the force of the needle striking the percussion cap, it deforms and detonates the primer. The primer then ignites the main charge, which then forces the bullet out of the barrel.

What is interesting about this cartridge is that the percussion cap is inside the middle of the cartridge and attached to the bullet. This means that the powder burns backwards towards the base of the bullet. In modern cartridges, the primer is usually placed at the end of the cartridge and hence, as the gunpowder is burning, the gunpowder closer to the bullet sometimes gets blown out of the barrel along with the bullet and some of the flash occurs outside the rifle. With the needle gun cartridge, the primer is in the middle and so the gunpowder burns towards the base of the cartridge and thereby burns all of the powder. In fact, since the cartridge was made of paper, the paper was almost completely burned as well and needle guns didn't need to clear the old cartridge case when loading a new one. Additionally, since the primer cap was attached to the bullet, it would be ejected along with the bullet. Due to the fact of the powder being burned completely, needle-gun cartridges often needed less powder than modern cartridges to propel a bullet to the same velocity. Also putting the primer in the middle of the cartridge made it harder to detonate the cartridge by accident.

When breech-loading needle guns were introduced around 1835, they were a massive improvement over muzzle-loaders in that the loading time was significantly reduced. A soldier using a Dreyse Needle Gun could reload 5 times before an opponent using the latest muzzle-loaders of that time and could do this from a prone position. This gave the Prussians a massive advantage over the Austrians. The French were not long behind making a needle-gun of their own. The needle-gun was the first widely adopted military breech-loading weapon, and was responsible for making muzzle-loaders obsolete from the military scene.

So why did the needle gun cartridges eventually get replaced by more modern cartridges? Well, one of the weaknesses of the needle gun cartridges was the firing mechanism. The needles were thin and delicate and broke often. As a result, soldiers needed to carry spare needles with them on the field. Also, the sealing mechanism on the breech wasn't always tight and sometimes the gas would escape from there and burn the soldier's cheek. Better options were invented for breech-loaders and the needle-gun and its cartridges faded into history by the 1880s or so.

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