Muskets & Springfields is designed for playing big battles in the American Civil War and is not model scale dependent and uses the player's current basing system. The game is set at the operational level. The player is the army commander with sub command groups. This will be typically a Corps. In these rules a Corp is made up of several infantry brigades, mounted cavalry, and artillery batteries. If you wish you can also include Native American Indian warbands.

The basic unit in wargaming terms is the infantry brigade, which are grouped into Corps or Divisions. The game system uses grids as the unit of measurement. The game space is broken into several square grids which represent 300 yards in ground scale. Taking a balance of the various drill guides of the period this is approximately equal to 600 men in two ranks. For a typical 6x4 playing space it is recommended a ratio width x depth of 1.5 x 1. A typical 6x4 table provides the following 12 (3600 yds) by 8 (2400 yds) of battlefield.

Morale is handled at the corps level and attrition is held at the individual unit base. These rules have three levels of morale. This is not the usual average, veteran, elite often used. Instead, the format is designed to reflect the actual state of mind on the day. These are Unknown, Nervous and Steady. In a game, unless representing specific historical units all bases start as Unknown. The actual morale state is not known till the unit takes damage. The player then rolls against a chart which provides a score for the unit being Nervous or Steady. This is dependent on the year being played and if Confederate or Union. When a unit fails a morale check this is recorded against their parent corps. Once a corps reaches its break point it will then flee the battlefield. Attrition is held at the unit level. This represents loss of cohesion, battlefield casualties or supplies running low. A unit can absorb 6 hits before it is automatically destroyed.

To facilitate a clean flow of play these rules also facilitate the use of sharpshooters and skirmishers. Turns use a bag-pull system in which it is possible for the non-active player to able to interdict the play.​