Usually, these muskets work best if the tang and the back 4 inches of the barrel are bedded. You really don't need to bed much more of the barrel mortise than that. This is different than bedding Modern rifle stocks and barrels, but the work is the same. If you have done the one you can do the other.
Before bedding anything, first put the barrel in the stock and screw down the tang screws to their normal position. Then try to insert the wedges or barrel pins in their slots/holes. If they don't line up, you have a problem with the bedding at the tang, or you are screwing the tang bolts down too hard! Back the bolts off, and see if the keys/pins don't go in.
Now, reverse the test, by putting the keys/pins in their slots/holes, and then see if the tang bolt or screw lines up with the hold in that mortise. If not, you probably need some bedding at the back of the barrel so that the various screws and bolts, keys, or pins are not working against each other.
I hope this helps, and explains the why's and how"s to those who have not tried bedding a barrel before. Frankly, the same test is used with modern rifles, and shotguns( to some extent), too. There is a particular problem in many of the hinged, or " Hooked " breech rifles on the market, as often the two metal surfaces don't mate well, and need some filing to fit properly. Even after they fit together well, bedding both the tang and the barrel to support those two pieces of metal will usually contribute to much greater accuracy, and particularly where that first shot out of a cold, clean barrel will impact.