The barrel was the typical 22” carbine length and rifled to use the .54 caliber Minnie ball.
It featured a captive ramrod that was retained by a swinging link system, similar to the pattern used on the US M-1842 pistol.
An interesting side note on this carbine;
In 1963/early 1864 the Confederate War Department contracted with Virginia arms maker, Bilharz, Hall & Co., to produce 1000 copies of the M1855. The only difference would be the caliber. Someone in the Confederacy must have thought highly of the little carbine.