Wubei Zhi (Vol. 55)

For every unit of ten, take one person. For instance, in an encampment of three thousand, use six hundred men to fire the Weiyuan Cannons, Thunder-clap cannons, and similar artillery. Of the remaining two thousand four hundred, order five-tenths to each carry one Firearm Staff, and five-tenths to carry fire-lances and swords or spears. These also use a sight gate xing men. The upper body is entirely made of iron, like a bird-gun niaochong matchlock musket, capable of firing once or twice. The lower body is an iron-linked core wrapped in bamboo, rattan, and lacquer. If there is time, fire it and then reload with powder; if in an emergency, use it as a blunt staff to strike. It is one implement serving two purposes. Each use requires three 1/10ths of a tael of powder and one lead pellet weighing three 1/10ths of a tael. Fired flat, it reaches over two hundred paces. Powder is only loaded when about to fire to prevent unforeseen accidents.

Military Records Treatise, Volume 122; Records of Military Provisions; Illustrated Treatise on Firearms, Part 7