Thanks.

No! The only muzzle loader that is expressly designed for smokeless (and only certain ones at that) as well as black/pyro. is made by Savage, not Marlin. If you value your life, avoid ANY form of smokeless powder in your Marlin.

I am curious about this as well. As xmp5744 is used in the black powder cartridges, it would seem that in a modern in-line using primer ignition if the pressure could be kept at black powder levels, it could be possible. That said, I am not willing to try it and would never recommend it.

MFH

I know there are a lot of people doing it,(using smokeless ) in knights and encores.If you do I would make sure you had your medical insurance paid up and will made out.Sooner or later someone is going to need it.
Think I will play it safe and use what was intended in mine.

Brent,

I should have been more specific. My curiosity was in using a T/C Encore. I realize the brass case helps to contain the pressures, but is nothing compared to the surrounding steel. Also, the closed breech should help, especially using primer type ignition. Either way, I have better things to do than try to deliberately screw up a gun.

MFH

BP cartridge rifles operate at breech pressures of up to at least 25,000 PSI. A muzzleloder should be kept below around 15,000 PSI. The reason for this is that the breeching of a muzzleloader cannot be as gas-proof as a rifle using a brass cartridge case and a well-supported primer. A cap won't contain as much pressure, and I have my doubts about a 209 primer, unless the striker mechanism is locked in place against the primer after striking it.