SDK
Your problem is that most muzzleloaders made today will not qualify in either of the 3 Pacific Northwest States.
When a friend of mine in Kennewick asked me the same question a few years back - my first thought then and the first suggestion now is still the same - "Get a White" Problem they are not being made anymore - but if you can find one get it - Underclocked is your best resource in this task...
My second suggestion would be another rifle no longer being made but you can pick them on the auction sites.... A Remington 700ml
Both the White and the Remington can use all three ignition system and this year in the state of Washington you can even use regular bullets in a sabot - both of these rifles will shoot Conicals and Sabots really well.
There is a rumor that TC is going to build a Pac Northwest compatible gun in the near future, but the way the economy is ????
If you are really thinking that a Traditional rifle will suit your situation them I would make the following suggestion and it is going to sound a lot harder than it is.
But I would suggest that you contact Green Mountain Rifle Barrels and buy a 50 cal GM-LRH barrel (long range hunter). Then off ebay or some other site purchase a TC Renegade or Hawkin stock - put the two together and you would have a great Traditional capable of shooting full bore conicals or sabots. This would make an excellent elk gun to 150 yards - limited only by the open sites that you have to use.
I honestly would not hunt an elk in our hunting situations with a 50 cal patched round ball. If you are wanting to use a round ball use at least a 54 cal. Not that a 50 couldn't do it but you would be terribly limited in range. Plus being a beginner shooter - shooting a PRB accurately is not something that just happens.
Where are you at in Washington? I am across the line next to WSU.