BigAL, you can even ship a centerfire rifle without an FFL. The key word is SHIP. Hence you cannot recieve one unless it is yours being returned from repair or service or you have shipped it to yourself (ie..hunting trip). But (in general) you must ship an firearm TO an FFL or to yourself, or and you cannot ship a firearm to an individual.
The ATF does not consider a Muzzleloader (with exceptions) a firearm.
These are my understandings.
Also be sure to check as some states have restrictions on muzzleloaders. (Kal, Mass, Maryland, NJ, NY, ??)
Trap55555