After going round and round with the owner, I acquiesced and took his word that the Merwin Hulbert I was repairing was a 44-40, not a 44MH, even though it was not marked Winchester 1873 on the frame like MH 44-40's were. He allegedly got this info through family documentation. I got some bp rounds from mazo, loaded one in the cylinder and gave it a spin to check for OAL, it bound up on the barrel. I went and trimmed about 2mm off the slugs, that was my only problem in loading, the bullets chambered fine. Took the revolver out back for a test run, fired six and it felt like I was shooting 44 magnum's !!!! Took the gun back to the shop to un load it, and the unloading procedure was impossible to complete. I finally pushed each shell back out through the loading port and the gun functioned properly again. That's when I discovered the problem, 3 of the cases had split and they all had a swelling at and below the neck and a compression ring on the top of the neck!!!!! A true testament to the quality of the revolver is that it incurred no damage. There is a step in the cylinder chambers, in front towards the bbl that shrinks the chamber opening to the correct diameter for the slug, not the casing. What I learned, besides listening to my gut, is that a 44-40 is 1.655 OAL and a 44MH is only1.16 OAL, the difference is in the case length and obviously the powder load.