Reportedly, 100 each of the Model 1841 "Mississippi" rifles, Model 1842 muskets, and Model 1847 cavalry musketoons were converted using James H. Merrill's breech loading system c. 1861-1862, according to relevant information on pages 172-175 of the book "American Military Shoulder Arms Volume III" by George D. Moller. The alteration of these Model 1841 rifles involved boring out the barrel and rifling it for use with .58 Minie balls, removing the original breech plug and installing the Merrill breech system as well as adding the lever catch to the barrel, adding a screw through the lock plate, and using a bolster with a cleanout screw. It has a brass blade front sight, three-leaf notch rear sight, "WW/P" and "V/P/(eagle head)" proofs on the left at the breech, the three-line Merrill maker, address and patent markings on the lever, standard Harpers Ferry markings on the 1848 dated lock, "JHK" and "R" inspector marked on the left stock flat. Includes an extra nipple in the patchbox.

Exceptionally fine, retains 85% original brown finish on the barrel, 70% plus original oil-quenched casehardened finish strongest on the lock and on the breech lever, with absolutely sharp markings and edges in the metal overall. The brass fittings retain an attractive untouched original bright golden appearance. Stock is excellent with attractive original raised grain, rich oil finish, some light handling marks and occasional minor dings, distinct edges, and exceptionally crisp inspector stamps. Mechanically excellent. This exceptional example of a rare Merrill breech loading U.S. Harpers Ferry Model 1841 "Mississippi" rifle would be very difficult to improve upon!