For A Few Dice More is a set of free wargames rules for wild west gunfights.
Dating to 1972, the Wargames Research Group’s 1750 – 1850 are primarily intended for the Napoleonic Wars. By modern standards they’re a bit dated, but my recollection is that they are fun.
Iron and Steam is a set of free wargames rules for pre-dreadnought Victorian naval actions.
Iron and Steam is a set of miniatures rules for naval combat of the American Civil War. The rules feature a gun-by-gun combat resolution, written orders and simultaneous movement. Traditionally played with 1/600 scale models the combat scale is closer to 1/2400 scale, though the game is generally model scale agnostic. Also included are over 100 pre-filled ship record sheets, turning radii and arc-of-fire templates as well as a 2 page QRS to facilitate fire resolution.
Here’s a set of free wargames rules for the Spanish American War using multiple dice sizes and designed for 28mm figures.
Edwardian Splendor is a set of free wargames rules for playing games with 54mm figures.