While late to the thread, I would also note that the early war photographic evidence regarding the 9th Mississippi, the photos from Pensacola, appear to reflect that at least one, and likely the flank companies were armed with Model 1855 Rifles and sabre bayonets. You'll also see stacks of Model 42 Springfield muskets identified to the 9th. Most photo captions will ID the rifles as "Mississippi Rifles" (Model 1841), but close observation will reveal a nosecap, as opposed to an upper band wrapping around the barrel and the Maynard primer lock.

Tom Cezanski, who used to be with the Louisiana State Museum informed me some years back that records reflect a number of Model 55 rifles from the arsenal in Louisiana were given to Mississippi -- likely the arms that ended up with the 9th, but I don't know what records he was citing.

Dave Neel