This topic comes up all the time, usually raised by some fellow who is sure he has found a "loophole" in the law that will let him carry a loaded gun. Sorry, it won't.
Revolvers that do not fire fixed ammunition (which is what it appears is really meant, not "black powder revolvers") are exempt from purchase and ownership restrictions under Federal Law and most state law.
But I know of no state handgun carry law, concealed carry law, armed robbery law, or assault with a deadly weapon law that makes any such distinction. Most of the those laws refer to a "handgun" or a "deadly weapon" and don't even mention the kind of gun or the type of ammunition.
(I recently read that when auto pistols were first invented, some folks discovered that many state and local laws on carry, robbery, or whatever, referred to "revolvers". So, the lawyers argued, if a "deadly weapon" law specified a revolver, an automatic pistol didn't count. The courts allowed the ingenuity of the argument and convicted the bad guys anyway.)
Jim