You are correct about the Lorenz Rifle. My postulation was based on the popularity and History of the Mississippi Rifle with Jefferson Davis and the 1st Mississippi Rifle during the Mexican American War and thus it was possibly readily available from Mississippi Arsenals considering the Confederate army was assembling in Northern Mississippi at about the time the 1st Arkansas was transferring there.

Short of a Quartermasters report who can be absolutely sure what they were armed with. But my guess would be the odds favored the Mississippi.