Black powder

Gunpowder is a substance which burns rapidly, used as a propellant for firearms. There are two types: black powder and smokeless powder. Almost all modern guns use smokeless powder. While black powder is classified as an "explosive", modern smokeless powder merely burns rapidly as described below.

Gunpowder burns, producing a subsonic deflagration wave rather than the supersonic detonation wave which high explosives would produce. This reduces peak pressures in a gun, but makes it less suitable for shattering rock or fortifications.

Smokeless powder consists of almost pure nitrocellulose (single-base powders), frequently combined with up to 50 percent nitroglycerin (double-base powders), and sometimes nitroguanidine (triple-base) corned into small spherical balls or extruded into cylinders or flakes using solvents such as ether. Smokeless powder burns only on the surfaces of the granules. Larger granules burn more slowly, and the burn rate is further controlled by flame-deterrent coatings which retard burning slightly. The intent is to regulate the burn rate so that a more or less constant pressure is exerted on the propelled projectile as long as it is in the barrel so as to obtain the highest velocity. Cannon powder has the largest granules, up to thumb-sized cylinders with seven perforations (one central and the other six in a circle halfway to the outside of the cylinder's end faces). The perforations stabilize the burn rate because as the outside burns inward (thus shrinking the burning surface area) the inside is burning outward (thus increasing the burning surface area, but faster, so as to fill up the increasing volume of barrel presented by the departing projectile). Fast-burning pistol powders are made by extruding shapes with more area such as flakes or by flattening the spherical granules. Drying is usually performed under a vacuum. The solvents are condensed and recycled. The granules are also coated with graphite to prevent static electricity sparks from causing undesired ignitions.

Black powder consists of the granular ingredients sulfur (S), charcoal (provides carbon to the reaction) and saltpeter (saltpetre, potassium nitrate, KNO₃, provides oxygen to the reaction). The optimum proportions for gunpowder are : Saltpetre 74.64%, Sulphur 11.85%, Charcoal 13.51%.

The basic ratio is:

2 parts Sulfur : 3 parts Charcoal : 15 parts Saltpetre

For the most powerful Blackpowder "meal" you should use a softwood charcoal, [such as balsa, or willow] and incorporate the ingredients as thoroughly as possible. This can be achieved using a ball mill with non-sparking media [ lead ], or similar device

Black powder is also corned to change its firing rate. Corning is a process which first compresses the fine black powder "meal" into blocks with a fixed density [1.7g/cc]. The blocks are then broken up into granules. These granules are then sorted by size to give the various grades of black powder. Standard grades of black powder run from the coarse Fg grade used in large bore rifles and small cannon though FFg (medium and smallbore rifles), FFFg (pistols), and FFFFg (smallbore, short pistols and priming flintlocks).

Although black powder is not a true high explosive, the United States Department of Transportation classifies it as a "Class A High Explosive" for shipment because it is so easily ignited.

History

Gunpowder was first discovered in China in the 9th century. The discovery appears to have been by accident by alchemists seeking the elixir of immortality, and the first references to gunpowder appear as warnings in alchemy texts not to mix certain materials together. By the 10th century, gunpowder began to be used for military purposes in China in the form of rockets and explosive bombs fired from catapults. The first reference to cannon appears in 1126 when oil bamboo tubes were used to launch missiles at the enemy. Eventually bamboo tubes were replaced by metal tubes, and the oldest cannon in China dates from 1290. From China, the military use of gunpower appears to have spread to Japan and Europe. It was used by the Mongols against the Hungarians in 1241 and was mentioned by Roger Bacon in 1248. By the mid 14th century, early cannons are mentioned extensively both in Europe and in China.

In China as in Europe, the use of gunpowder to produce firearms and cannon was delayed by difficulties in creating metal tubes that would contain an explosion. This problem may have led to the false myth that the Chinese used their discovery only for the manufacture of fireworks. In fact, gunpowder powered cannon and rockets were extensively used in the Mongol conquests of the 13th century and were a feature of East Asian warfare afterwards. The short squat and thick city walls of Beijing for example, were specifically designed to withstand an artillery attack, and the Ming dynasty moved the capital from Nanjing to Beijing specifically because the hills around Nanjing were good locations for invaders to place artillery.

The 15th through 17th century saw widespread development in gunpowder technology both in Europe and the Far East. Advancements in metallurgy led to small weapons and the development of muskets. Cannon technology in Europe gradually outpaced that of China and these technological improvements transferred back to China through Jesuit missionaries who were put in charge of cannon manufacture by the late Ming and early Qing emperors.

Smokeless powder

In 1886 Paul Vieille in France invented a smokeless gunpowder called Poudre B. Made from gelatinized nitrocellulose mixed with ether and alcohol, it was passed through rollers to form thin sheets, which were cut with a guillotine to flakes of the desired size. Vielle's powder was used in the Lebel rifle that was adopted by the French Army in the late 1880s.

The French Army was the first to use Poudre B but it was not long before other European countries followed their example. Vieille's powder revolutionized the effectiveness of small guns and rifles. Firstly because practically no smoke was formed when the gun was fired and secondly because it was much more powerful than black powder, giving an accurate rifle range of up to 1000 yards.

In 1887 Alfred Nobel also developed a smokeless gunpowder. This eventually became known as cordite, a powder easier to handle and more powerful than Poudre B.

Smokeless powder allowed the development of modern semi- and fully automatic firearms. Burned blackpowder leaves a thick, heavy fouling which is both hygroscopic and corrosive. Smokeless powder fouling exhibits none of these properties. This makes feasible an autoloading firearm with many moving parts (which would jam or seize under heavy blackpowder fouling).

Reference

• Gunpowder: Alchemy, Bombards, & Pyrotechnics by Jack Kelly - New book that covers the history of the explosive that changed the world (Basic Books, ISBN 0-465-03718-6).