Custom shop barrels are no longer available. All parts inventory was lost in the factory fire. For a time, SSK Industries still had some parts and made barrels, but those are gone now, too. No new barrels.
When the TCR first came out, it was only for standard calibers. Later, some frame modifications were made so that it would handle magnum calibers, and I believe something about the barrel fit was changed so that the magnum barrels would not fit on the old frames, but old barrels would fit on magnum frames. Maybe someone else here knows more particulars about the magnum frame thing.
Hope this helps you.
RonF