The M1841 Mississippi Rifle was a percussion lock rifled musket manufactured by the Harpers Ferry US Armory from 1841 to 1861. The M1841 was significant in that it was the first percussion lock rifle used by the United States and became synonymous with the volunteer regiment known as the "Mississippi Rifles" (now known as the 155th Infantry Regiment of the United States).
The M1841 Mississippi was conceived in an era dominated (in the US) by the various designs churned out by the Springfield Armory. As such the M1841 was very close in design to the Model 1835 Musket (itself an evolution of Springfield's Model 1822) and the two designs shared the same stock design.
The Mississippi, however, featured a rifled barrel and became, therefore, a rifled musket and one of the first rifled firearms to be weilded on a large scale by any American force. The barrel itself was made from iron and cut with a rifling twist ratio of 1:66in (ie 1 twist in every 66in). The Mississippi's barrel also lacked a bayonet lug, therefore meaning that a bayonet could not be fitted to it (a consideration that was taken due to the fact that the Mississippi effectively had a greater effective range).
The Mississippi was made more unique with the addition of sights. The addition of a v-notch sight (on the earliest examples) was a novelty at the time, as most muskets lacked sights as the range at which they could achieve accurate fire was around 50 yards at the most, and therefore the need for sights was non-existant. Later models of the Mississippi were fitted with either leaf sights (graded from 100yds to 500yds) or ladder sights (graded in 100yd increments from 100yds to 1,100yds). These models were also fitted with a sword bayonet.
The Mississippi rifle was first chambered for the .54in (13.7mm) musket ball, the standard calibre size for the American military at that time. From 1855 the Mississippi was produced (and often converted) to fire the .58in (14.7mm) Minie ball (as, again, this was the standard calibre at the time across the American Armed Forces). Both calibre sizes were shot from a paper cartridge.
The M1841 rifle was designed at the Harpers Ferry US Armory in 1840, during the Armory's guidance by Eli Whitney Blake. It came at an early stage of transistion for the US Military as the introduction of rifled weapons to the main body of men was a couple of years from beginning, although the Armories (at Harpers Ferry and Springfield) had already begun work on rifle/musket designs.
The M1841 was first ordered by Jefferson Davis (the future President of the Confederate States of America), whom went against his commanding Officer General Winfield Scott by using the rifled muskets. The M1841 caused the long standing feud between the two men, especially after Davis got approval from President James Knox Polk, and also led to the name "Mississippi" after Davis' regiment, The Mississippi Rifles.
The first use of the newly cristened Mississippi rifle came during the American-Mexican War. Specifically, during the Battle of Buena Vista, Davis' regiment led a push against the Mexican force that effectively won the battle (and earned Davis the rank of Brigadier General, a rank which he declined). The Mississippi would continue to be used through until the conclusion of the American Civil War by members of both sides (most notably, though, with the 45th New York Infantry).