David, I've owned two. The first was the Navy and I had the top portion of the hammer break. There is a little lever that allows you to pivot the tip of the hammer down in order to strike the shotgun nipple. The way this is made, there is a portion of the hammer in the middle that pivots, leaving two "ears" which are rather thin. These are a little frail and mine broke.
I returned it in exchange for the Army model in which the entire tip portion of the hammer pivots, rather than simply the middle portion.........
You know what, I don't know if this is making any sense. Let's just say that I feel the Army model (same as the Cav model except for the trigger guard) hammer is a stronger design than the Navy Model - in my experience anyway.
The only problems I have come across are ......
1. Anything more than about 22gr of BP (or Pyrodex) is gonna make the loading lever flip up. Kind of like the loading lever on a Walker dropping down. Nothing more than a small pain in the rear.
2. I once was shooting my LeMat and Ruger Old Army. I made the mistake of not paying attention and used the .457 balls in the LeMat and bent the loading lever a bit. It uses .454 balls. The Ruger uses .457.
Other'n that it's incredibly accurate, moreso than any other BP pistol I've owned.
I've never shot the shotgun bbl as, well, I just never have.
Seeing as how Navy Arms no longer offers them from what I can tell, it seems the only place to get one is from Dixie Gun Works. They're going for around $800.00 now. You can get replacement parts for them through Dixie as well (like a replacement loading lever ).
I got mine from a friend as a gift when Navy Arms was blowing them out for around $350.00 about 10 years ago. If it's in good shape and an Army model (or better yet, the Cav model - they do look good!), I'd get it.