In our gaming group, we have been developing our ACW rules for many years. I am a strong proponent of the idea that developing your own rules is an integral part of the hobby, and that it allows you to try out many experimental rules mechanisms that otherwise would probably never be used on the gaming table.
We started with this ACW ruleset somewhere in 2006. Before that, we used very often the Brother against Brother rules by HG Walls. This is a rather simple ruleset, originally designed for fast convention games. The basic unit is designated a squad. Squads were activated by drawing cards, and combat strength for each unit was directly proportional to the number of figures. Our rules are still called "Brother against Brother" - we should probably change that sooner or later.
However, to our tastes, BaB was a bit too simplistic and too much geared towards 'fast effects'. So we started to tweak the rules over the years. One of the first things was to streamline the morale system, and we replaced the morale cards with three different tables depending on the situation in which a unit finds itself. Roll a D20, cross-reference the with the current combat strength, and you see the result.
Another major change was the activation system. Drawing a card every turn to indicate what unit can move is all well for games in open fields, but that mechanic can create choke points during movement, and it is difficult to coordinate multi-unit actions. We experimented with Piquet-like activation systems; with written orders; but finally settled on an activation sequence similar to Black Powder / Warmaster / Blitzkrieg Commander. It has served us for many years, and now really forms the heart of the rules.
Unit sizes are not specified. We still refer to unit as 'squads', but sometimes our scenarios do much more have the feel of skirmish games, sometimes the are closer to big battles. It strongly depends on the scenario setup. In this respect, we are very similar to the philosophy in games like Black Powder or Hail Caesar, two rulesets we also happen to play quite often.
Other changes made over they years are the elimination of many modifiers in the combat resolution engine. I strongly believe in the idea that wargame rules should be as simple as possible (but not simpler :-)). There is no challenge in writing a ruleset with plenty of complicated rules, plenty of die roll modifiers, separate procedures for all sorts of actions. Anyone can do that. It's much more challenging in designing a ruleset that is as simple as possible, but still creates the look-and-feel of the period in question.
Is this ruleset able to recreate ACW actions ina plausible manner? Honestly, I do not have a good idea. It is probably too simple for connoisseurs of the period. But for all the players in my gaming group, which are well versed in military history (ACW is just not one of our fortes), it is an acceptable, fun, and reliable ruleset. It allows us to finish a game with 10-20 units on each side within a single evening, a VERY important advantage. And we are having fun. In the end, that is what really counts.
So, below are the rules. Please download them, and let us know what you think.
==> (update October 22, 2014): Please refer to the ACW House Rules page where you can find the latest developments.