The Mississippi rifle was the first standard U.S. rifle to use a percussion lock system. Percussion lock systems were much more reliable and weatherproof than the flintlock systems that they replaced, and were such an improvement that many earlier flintlock rifles and muskets were later converted to percussion lock systems.
The Mississippi rifle was originally produced in .54 caliber, using 1:66 rifling and no provision for fixing a bayonet.
In 1855, the Mississippi rifle was changed to .58 caliber, so that it could use the .58 caliber Minie Ball that had recently become standard. Many older Mississippi rifles were re-bored to .58 caliber. The rifle was also modified to accept a sword type bayonet.
The first Mississippi rifles had a v-notch sight. This was later replaced with leaf sights with 100, 300, and 500 yard ranges. A ladder sight with ranges from 100 to 1100 yards in 100 yard increments was fitted on some later rifles.