Science fiction set in alternate Victorian timelines (“Steampunk”) interests many people and there are several works of fiction such as Bruce Sterling’s and William Gibson’s “Difference Engine” and several of Michael Morcock’s books, notably the “Nomad of Time” trilogy.
There are also several games based on the idea.
Below are a couple of wild ideas from myself and my friend Ed.
A New Small Arms Rules System for Space 1889.
This gives a more realistic and detailed game than the original rules without making things unduly complex. Using this system you can adapt any weapon of the period to the game.
Some Information on 19th Century Small Arms.
Some of this was taken from Albert Lowe’s gun files at http://www.space1889.org/
I’ve corrected a few minor errors and added a lot of additional weapons and some historical and technical information.
Information on additional hardware likely to be found in Steampunk 1920 games.
Some of my ideas on Conveyances
Two Descriptions of typical Martian garb.
Lord Edward’s Ideas to Modernize Warfare.
Other sites
Not a game site, but plenty of information on some of the weapons likely to be encountered.