Here are a set of rules from the man who is arguably the “Father” of American Wargaming, Jack Scruby: Basic Wargaming Rules.
horse and musket
19th Century Square Brigadier Rules
Ross McFarlane’s 19th Century Square Brigadier rules are designed for late 19th Century wargames on a square gridded battlefield.
Wargames Rules 1685-1845
Wargames Rules 1685-1845 is a set of classic WRG rules from 1977. I own a copy, but you can get your own in pdf form at the link.
Hearts of Tin Horse and Musket Rules
Ross Macfarlane offers Hearts of Tin, a set of simple Horse and Musket rules:
Volley Fire 2mm Rules
Volley Fire is a set of 2mm wargames rules,
designed for lots of volley firing infantry with rifles, horse and cannon. It is meant for simplicity, so ignores morale and commanders and such likes, but maintains a certain amount of realism in certain areas. These can be written in at a later time. I’m very open for suggestions. Anyhow, on with the tour!
Each player has an army consisting of several companies of infantry or cavalry, and batteries of artillery. Infantry companies are made up of one to five platoons, cavalry of a similar number of squadrons, each of which is represented by one strip of models. Artillery batteries consist of a similar number of guns. Units can be either Close order (c.o.) or skirmishers.