James Merrill was a Baltimore inventor and businessman who patented an improvement to the Jenks pattern carbine in 1858. His idea was for an improved locking lever for the gun, which would also allow the use on paper or linen cartridges instead of loose ball and powder. He demonstrated the improvement at the Washington Navy Yard in 1858, and received a contract to convert 300 of the Navy Jenks carbines to his new system.

He did so, and had his guns almost immediately returned to him, as the springs in the lever latch were apparently too weak. He fixed this problem, but only submitted 240 carbines back to the Navy (the reason for the 60-gun loss is unknown). He received no further orders, but he did produce a new-manufacture carbine using the same patent which he sold to the Army during the Civil War.