On a cartridge firing rifle, anything touching the barrel can affect accuracy. Some shoot better with the barrel not touching anything forward of the reciever and some shoot better with some upward pressure at the end of the forearm. I don't suppose a muzzle loading rifle is any different, the same physics apply, but most of them have heavier barrels which tend to minimize vibrations. I wouldn't think it would make much difference unless there was extreme pressure as from a warped stock. I'm not familiar with your rifle. If it has the barrel secured to the stock by a wedge you should be able to tell something by how much tension is on it when it is tapped out. It couldn't hurt anything to relieve wood from the barrel channel so the wood isn't touching the barrel except where it has to bear for attachment to the stock, but most muzzle loaders just aren't designed to have the barrel free floated.
A fun test you can do sometime about barrel contact. Shoot a group with a well zeroed rifle for a control. Then shoot another group while someone rests something, a screwdriver for instance, on top of the barrel. Shoot groups with the assistant applying pressure from each side. In every rifle I've done that with, I have gotten 4 distinctive groups. It will work with a .22 also. It demonstrates that barrel harmonics are affected by contact. As long as that contact is constant, though, the grouping shouldn't move around.
Steve
A fun test you can do sometime about barrel contact. Shoot a group with a well zeroed rifle for a control. Then shoot another group while someone rests something, a screwdriver for instance, on top of the barrel. Shoot groups with the assistant applying pressure from each side. In every rifle I've done that with, I have gotten 4 distinctive groups. It will work with a .22 also. It demonstrates that barrel harmonics are affected by contact. As long as that contact is constant, though, the grouping shouldn't move around.
Steve