A while back I got on my soap box about trying to figure out all 50 states muzzleloader rules.... and the major head ache that it gave me. You can read that blog post by clicking here if you desire.
I was really frustrated to see some states mandating out of date methods and propellants that are just not as safe as modern methods and propellants. The State of Washington had some of the worst in my opinion. I was glad to see that the Washington Fish and Wildlife Commission proposed a rule change to allow sealed breeches and modern primers. I didn't see this until the comment period was closed. And now I just read through the rules for 2018: The change has been adopted! You can use our sealed breech 209 system in Washington now! (UPDATED!)
(look at Page 87 of the Washington Hunting regulations linked above, the update allowing 209's and getting rid of the exposed ignition is in red)
However, if you only hunt in places that allow sealed breeches (which is 48 out of 50 states now!), it's always cheaper to convert your bolt than to purchase an entire new bolt. It's always best to have a sealed breech: it stops blow back from getting into nooks and crannies and protects the shooter!