Stargrunt 40,000

Stargrunt 40,000 is a system for converting Warhammer 40K army lists into a format usable with Stargrunt.

Warhammer American Civil War Variant

The Cops.NU site has a Warhammer 40K variant for the American Civil War. I think it could work.

Three Musketeers Legends of the Old West Variant

Sgt. Perry’s Heroes offers a variant of the Legends of the Old West rules for miniature wargames set in the era of the Three Musketeers.

Gemini Rules For Warhammer 40K

The Gemini rules for Warhammer 40,000 are essentially a set of house rules for Games Workshop’s flagship product.

I think that the author is correct in his premise — that the Rogue Trader rules were perhaps the best.

GrimDark Racing One Page Rules

GrimDark Racing is a set of simple rules for races in the Warhammer 40K universe. Just use models you already have. There’s plenty of violence, of course.