there are muzzle loading magazines out there. Many of them like Muzzle Blast deals with traditional rifles and the way of the mountain man. A very interesting magazine. I used to subscribe to it. There used to be one called Black Powder that I saw on the stands from time to time. Whether it is still there, I have no idea.
Actually you can learn a lot about muzzleloaders on these forums. The magazines I found have turned into nothing but advertisements. Look through a magazine and really look. 2/3rd of it is adds in some. That is how they make their money.