Some folks argue that you should buy the Encore as a "pistol" but upgrade to a rifle, but not to buy a rifle and convert it to a pistol. This is in order to stay within the boundaries of an old dinosaur law set up by the BATF during the old gangster days. I really don't think it makes any difference (legally) as long as you DON'T put a rifle stock onto a pistol-barreled frame. That would be altering a rifle to have a "less than 16" barrel", which is illegal.
There's no difference at all in the frame between the rifle, pistol, shotgun, or muzzloader. The only difference is the stock and barrel. The barrels and stocks will interchange.