Cordite is a form of smokeless explosive propellant, invented by the British scientists Sir Frederick Abel, and Sir James Dewar in 1891, as an improvement over Alfred Nobel's Ballistite. It is used to propel bullets, large artillery shells, and even in solid fuel rockets.
The problem with Ballistite, and other explosives used at the time, was that they tended to become unstable over time. When you're dealing with explosives, you really really only want them to go off when they're supposed to. Nobel's mix was 45% nitroglycerin, 45% collodion, and 10% camphor. The camphor would eventually evaporate, leaving the mix quite unstable, causing accidents and costing lives.
So, the British Explosives Committee got together, and improved the design. Abel and Dewar patented their design of 58% nitroglycerin, 37% guncotton, and 5% vaseline. Mixed with acetone, it is formed into thin rods, which when the acetone dried was called "cord powder", quickly shortened to cordite. They'd vary in thickness from about 1mm to 5mm. Thinner rods were used for guns, whereas the thicker rods were used for artillery. Generally, the thinner the rod, the faster it would burn, but the less power it would release.
Now, this composition is rather similar to Ballistite, and as a result Nobel tried to sue for patent infringement. He lost because collodion, while quite similar to guncotton, is soluble, and his patent specified "of the well-known soluble kind". Guncotton on the other hand, is insoluble. And so, his lawsuit failed. Sucker.
One problem with the initial Cordite mix was that it tended to corrode gun barrels. To fix this, they changed the mix to 65% guncotton, 30% nitroglycerin, and %5 vaseline. This version, called Cordite MD (For MoDified), was introduced by the British military right after the 2nd Boer War. It doesn't burn quite as hot, but burns faster. The lower temperatures generated reduced gun barrel erosion.
During WWII, the formula was revised once again, this time with the addition of some new ingredients. Cordite N, or triple base powder, is made of 55% nitroguanidine, %19 guncotton, a bit under 19% nitroglycerin, and a bit more than 7% ethyl centralite. The nitroguanidine produces nitrogen when it goes off. This reduces muzzle flash, as well as keeping temperatures further down, reducing wear on the barrel. And Ethyl centralite is used as a stabilizer instead of vaseline, further decreasing the chance of accidental explosions.
Cordite N is created by mixing the Guncotton and the nitroguanidine, which is then mixed with an acetone nitroglycerin mix. After this is all mixed together, the Ethyl centralite is added. At this point the mix is jelly like. It is extruded into the thin rods, which are cut to the specified length. Then, the rods are dried, evaporating the acetone. I would imagine the production method for previous versions of Cordite were quite similar.
Cordite tends to be more stable than its counterparts, as well as burning a fair bit cooler, with less wear on gun barrels than most other forms of gunpowder. It is waterproof, and is stores well even in elevated temperatures. The components used to manufacture it are less expensive, although the manufacturing process is more complicated than most. It is most widely used by the British military, although it is used by other countries and individuals throughout the world.
Sources:
United States Naval Academy, "Chapter 2 Explosives," GENE SLOVER'S US NAVY PAGES. <www.eugeneleeslover.com/USNAVY/CHAPTER-2-1.html> (December 20, 2004).
Wikipedia, "Cordite," Wikipedia, the free encyclopedia. December 9, 2004. <en.wikipedia.org/wiki/Cordite> (December 20, 2004).
"CORDITE." LoveToKnow 1911 Online Encyclopedia. © 2003, 2004 LoveToKnow. <100.1911encyclopedia.org/C/CO/CORDITE.htm> (December 20, 2004)