couger,
You should consider getting a T/C Black Diamond. They are legal in Washington. As Keith said, the Encore wouldn't be legal even if it had the capability of using musket caps because of the closed breech. I just recently bought a Black Diamond and will be using it to hunt elk here in Washington this fall. I've put about 80 bullets through it so far and I'm happy with it, and don't think I will have any problem killing an elk with it this year.