The Huolong shenqi zhenfa 火龍神器陣法 "Fighting methods with the divine weapons of the fire dragon" is a military treatise on firearms written by the Ming period 明 (1368-1644) general Jiao Yu 焦玉. The book was finished in 1412, but later prints include material apperantly added at a later date. It is only one juan "scroll" long and includes 47 illustrations.
The book describes the fabrication of gunpowder, different types of firearms, their functions and use. Concerning the production of gunpowder, there had been made successes in comparison to the description in the Song period 宋 (960-1279) military encyclopedia Wujing zongyao 武經總要. In the Huolong shenqi zhenfa, only four components are used (instead of 14 components in earlier times), and the share of nitre (xiao 硝) has been increased from 49 per cent to 72 per cent, that of sulphur (liu 硫) lowered from 25 per cent to 16 per cent. The share of charcoal (mutan 木炭) is 11 per cent. These are the percentages for cannon gunpowder. For muskets, the adequate percentages are 77, 8, and 15. There are three different kinds of firearms described, namely combustives, explosives, and barrel weapons. Among the combustives are types already known during the Song period, including such producing smoke, or such spreading poisenous aerosols or gases. Among the explosives are grenades or various types of mines. Typical firearms with barrel are heavy muskets and cannons, but also rockets. During battle, the use of firearms is dependent of the weather and the territory, but also from the actual situation. There are long-range firearms (cannons, muskets, rockets), and short-range firearms (lances etc. with burning tips).
Source: Sun Deqi 孫德騏 (1989). "Huolong shenqi zhenfa 火龍神器陣法", in: Zhongguo da baike quanshu 中國大百科全書, Junshi 軍事, vol. 1, p. 419. Beijing/Shanghai: Zhongguo da baike quanshu chubanshe.