Don't think so, You can check the regs and make sure. I think it says something about having to be a single shot. I thought about buying a black powder double rifle one time and didn't for that reason.
Muzzleloaders: .44-cal. or larger, or muzzleloading shotguns 20 gauge or larger.
Primitive Weapons: Legal weapons during primitive weapons season include crossbows (scopes legal), bow and arrow, and muzzleloading firearms. Muzzleloader hunters must use iron sights or peep sights (fiber-optic material is OK) during primitive weapons season. Scopes and other optical sighting devices may not be used during the primitive weapons deer season.
I'd say it's legal as long as it's over the .44 cal requirement.
Raghorn, you should have got the rifle. One of my uncles and two of my cousins hunt w/ double barrel .50 cal. muzzleloaders. They've killed a bunch of deer w/ them over the years and really like them (you may have ran into them at one point or another as they've been hunting John's Mtn WMA and surronding areas since the late 60's, early 70's).
I once met a guy at Ogeechee that was hunting w/ a beautiful, custom-made double barreled flintlock. That was one fine weapon.