The rifle is a civilian half-stocked arm, probably used for hunting. It does have a backsight of some sort which may have ranged flip sights attached, so is likely to be a rifle. Many CSA initially armed themselves with anything available,including shotguns of various types, The knife - as many have said in other threads - was often a photographers prop or something they bought locally - a 'soldiers weapon'. It probably ended up getting dumped on a long march - far too heavy and cumbersome!
This is my 'cleaned' image of Rhea's link = Sgt. Andrew Martin Chandler (r) with his family slave, Silas Chandler
View attachment 518304
Taken in 1862, the knives and the shotgun were their's but the pistols may well have been props (pepperbox, Colt Navy and a Beaumont Adams 100-bore). Most early photos show their subjects with large knives and pistols - with few military rifles and equipment seen. They had joined the Palo Alto Confederates, later the
44th Mississippi Infantry Regiment.
Both made it through with Sgt Chandler captured early on by the Union (Camp Chase OH) before exhange and rejoining the regiment then getting seriously wounded at Chickamauga (d 1920). and Silas went through unharmed and made a name for himself as a carpenter in West Point MS after the war (d 1919).
(full story:
https://www.loc.gov/rr//print/coll/SoldierbiosChandler.html)