My Black Diamond XR and Knight Wolverine II both use #11 caps to fire them off. All you do is stay away from pellets. You can also get a musket cap nipple and use that which actually is hot enough to set pellets real well.

Knight also makes inlines like my Knight Disc which you then get a #11 adaptor and use the #11 instead of the 209 primers. The place I think you might have a problem is in the break open models. Also be sure and check to make sure that the inline does not require an exposed breech. Then the Knight Disc is no good. If I wanted an inline that could shoot #11 caps and still had an exposed breech go with the Knight Bighorn. It is the same thing as my Wolverine II in a magnum version with a longer barrel. They are just an excellent rifle to carry and to shoot. They are easy to take care of and meet all the requirements of the states like Idaho, Colorado, and Washington I believe...