I found this image at the Smithsonian Institute, and thought it was very cool. I’ve never seen this type of gun before, and I suspect that the breech was less than sealed. Still, very cool.

Photo by: Hugh Talman Provided by: Smithsonian Images
American made sliding breech block which is also called a harmonica lock. It is a 5 shot, pill ignition. Inscribed “Houston.” This rare Henry Gross rifle belonged to Sam Houston.