Except it’s not really a gun. Well, sort of. According to the BATFE, blackpowder firearms are not “firearms”, which means they can be transferred between individuals across state lines without a 4473 form.
I’m currently selling my Pietta clone of the ’58 Remington, which is a .44 cap-and-ball revolver. However, what makes this gun cool is that with the pistol, I’m also selling a Kirst Konverter, a 5 shot SASS legal cylinder which allows you to fire cowboy action .45 Colt loads through the gun. Check out the auction on Gunbroker.