They are, except for the G-2 blackpowder barrel. From what I gather there is a pattent thing regarding T/C and the Contender and a maker of a BP barrel, Gonic, for it. No other factory can make a BP barrel for the Contender other than Gonic. Well, a new name (G-2) and a new set of rules. Now T/C can make a BP for the G-2, but not the Contender so they added a pin to the bottom of the barrel and a hole in the G-2 frame that accepts it, whereas the Contender can't.

Simple solution is to remove the pin from the barrel and it fits all frames. Of course you'll "void your warranty" but WTH, you got blackpowder ;-)