I heard back from the regional biologist. Muzzleloaders are legal for small game - no restriction on caliber, scope, powder type, or bullet type. Therefore you can use a muzzleloader to hunt feral swine during a small game (squirrel/rabbit) season on a WMA. Just check the WMA permit/map under permitted firearms. Remainder of seasons will probably cover small game, and "Legal arms and ammunition as defined in 220-2-.02" allows muzzleloaders.