Adam,
I'm sorry for your bad luck, but glad that you found the crack now and not later, when it may have made it harder to get him to take it back. The gun exhibits a nice level of exterior finish in the photos, but the inside of the locks should have a higher level of finish. They are a bit crude looking , if the photos accurately portray what appears to be just a lack of time and handwork. I would not be at all surprised if the steel is soft in them.
It all may be a blessing in disguise, and certainly a learning experience.
