You may want to check this out.

http://www.badbullmuzzleloaders.com/faq.htm

They recommend huge amounts of 4350. 100gr minimum Thats WAY more than any of my SML loads with other powders including BH209. Other powders might be safe but 4350 is a very slow burning powder. Bad Bull says no other smokeless or sub powder may be used. Pellets are ok though.

They are made mainly for sabotless use and have a muzzle brake which isnt usually good for sabot accuracy. It might be removable if you want to shoot sabots but do they have any other load data besides 100gr or more of 4350?

It falls under the same regulations as a CF unlike more commonly sold SMLs.

LRM primers are press fit into a breach plug?

The only one that i like is the FB model based on a Ruger #1 because you can build a similar bolt gun on a Savage or Rem ML action for well under $1300. Ruger #1s can be pretty pricey unless you get lucky. Right now a guy is making a custom bolt nose for CF conversions that only requires a 209 for ignition.