Elegant British game designers Cakebread and Walton have released for free their 139-page d100 engine for Renaissance-themed frp gaming. The system is aptly titled Renaissance and may be downloaded from their web-site.
I haven't had time yet to fully scrutinise it, but I believe this rule set should be >95% compatible with The Celestial Empire and hence an interesting, free alternative to the purchase of Chaosium's Basic Roleplaying (BRP) System.
Renaissance features a lengthy section on Black Powder weapons and should hence be a welcome addition to any Qīng-dynasty games.
Renaissance also features a fully-fledged, spell-based alchemy system. Now, I am not in favour of magic-based alchemy systems (I'd rather manage alchemy as a set of mundane skills), but until I produce Chinese Alchemy rules for The Celestial Empire, it might be a good idea to try and use Renaissance's alchemy sytem -- with the obvious modifications for China, such as replacing the Philosopher's Stone with the Pill of Immortality. The Alchemists' Spells listed in Renaissance could be considered as a sub-set of The Celestial Empire Daoist spells.