Dear Mr. Wojcieszak,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located five series titled Letters, Endorsements, and Reports Sent to the Secretary of War, 1812 - 1889; Registers of Contracts and Orders for Ordnance and Ordnance Equipment, 1861 -1897; Ledgers of Receipts in Connection with Orders and Contracts for Ordnance and Ordnance Stores, 1861 -1881; Press Copies of Letters and Endorsements Sent to the Secretary of War, 8/1861 - 2/1903; and Contracts for Ordnance and Ordnance Supplies, 1812-1910 in the Records of the Office of the Chief of Ordnance (Record Group 156) and one series titled Contract Proposals, 8/1861 -12/1862 in the Records of the Office of the Secretary of War (Record Group 107) that may contain information about James H. Merrill and his rifle. For access to and/or copies of these records, please contact the National Archives at Washington, DC - Textual Reference (RDT1) via email at firstname.lastname@example.org.
We hope this is helpful. Best of luck with your research!