Gerard De Gre and Charles Sweet were pioneering wargamers who produced a number of rules sets, including these Rules For Napoleonic Wargames, which is played on a 4 inch grid.
napoleonics
Old Trousers 6mm
From Baccus miniatures, Old Trousers 6mm is a set of quick-play Napoleonics, played on a 2 foot x 2 foot board.
Muskets and Moustaches Napoleonic Miniatures Rules
Muskets and Moustaches (sic) is a set of miniatures rules for the Napoleonic era. The author writes:
It is a very simple game to play, all based on a handful of dice and rolls of 1-3 and 4-6. Obviously there is a bit more to it, but that is the essence!
Mini Nap 6mm Napoleonic Wargames Rules
Mini Nap is a set of Napoleonic Warfare rules for 6mm figures. The authors write:
MINI-NAP is a set of wargames rules specifically designed for playing a reasonably quick corps sized Napoleonic wargame using the 6 mm scale.
They grew out of my desire for a set of rules that would allow two players to play a traditional style, historically based Corps sized game (of around 35 to 50 units on each side) but one that would allow such a reasonably large game as this to be played and finished within about four hours (which they do).
Under the MINI-NAP rules, the basic force normally fielded is a Corps consisting of several Divisions. Unlike many other wargames systems, there is no points system involved in MINI-NAP. Players are encouraged to use an actual historical corps (and historical corps structures). That means you will need to do some research.
As a guide, the MINI-NAP Corps Guidelines give some general details on how many of the various nationalities involved in this period arranged their Corps (and also the Infantry Brigades, Cavalry Brigades, Mixed Brigades, Reserve Brigades and Reserve Artillery of the Divisions therein) and they also include how to rate units. Brigades are important within the game system.
Individual units manoeuvre, fire, fight hand-to-hand combat, etc, during the course of the game by the Brigade, as they did historically. Several Brigades can also manoeuvre by the Division if circumstances allow.
Grand Army
In 1975, Don Lowry released a set of rules called Grand Army. Designed for 9mm !? and 15mm figures, it allows players to recreate large scale battles for Napoleonics and the American Civil War. Grand Army now is available online.