The Minié ball or Minie ball is an ammunition type that was developed by Frenchman Claude Étienne Minié that replaced the musket balls used in muskets. The major change in design came from the use of a bullet shape and spin stabilizing due to the use of rifling in the barrel.
The Minié ball was made out of soft lead (the normal material for ammunition at the time) in a conical bullet shape (for aerodynamic purposes to increase velocity). The bullet also featured a lead skirt, designed to deform when the powder ignited and fill the space between the barrel and the bullet. The Minié ball was then engaged with the rifling and would start to spin. It also cleared some of the debris and fouling from the previous shot.
The Minié Ball was, therefore, designed to be smaller than the bore of the barrel it was shot from. This was so that the Minie ball could be loaded quickly and avoid the fouling produced by previous shots.
The base of the Minié ball was hollow, so that the powder would be forced into the Minie ball when it was pushed into the barrel by a ramrod, ensuring as much of the force produced by the powder explosion entered the Minié Ball.
Early examples of the Minié ball featured grooves cut into the Ball, designed to improve the stability of the bullet in the air. However this process increased the production time of the Minie ball and the process was dropped without a significant impact on accuracy.
The Rocket Ball and Volcanic Ball were later developments based on the Minié ball design.
The Minié ball was immediately seen as a more potent ammunition than its predecessor, the musket ball. The use of rifling and the bullet shape improved the stability of the Minié ball and therefore improved its accuracy. From its release in 1847 the majority of muskets, particularly those whose usage had extended into the Mexican-American War (such as the Model 1795 Musket) were converted to fire the Minié ball with the first, purpose built firearm designed to fire the Minié ball becoming the Minié rifle of France in 1847.
Muskets to be converted to fire the Minié ball were:
- Model 1795 Musket
- Model 1812 Musket
- Model 1816 Musket
- Model 1822 Musket - Provided with a thicker barrel for the process of rifling
- Model 1842 Musket - Provided with a thicker barrel for the addition of rifling, sights fitted during the conversion
The first purpose built weapons to use the Minié ball were:
- Minie Rifle - France (Named for the Minié Ball)
- Enfield Pattern 1853 Rifled Musket - Britain
- Springfield Model 1855 Musket - USA
The Minié ball saw its greatest use during the American Civil War as well as the Crimean War, gaining its reputation for being an accurate and quick-loading round.