Actually, I'm not sure it's a SB2 frame, but it should be OK. That was the question I called NEF about. My question was "will the reciever in the new 3 barrel combo's be compatable with the barrel accessory program." (because they are listed as SC3-XXX, not SB2-XXX, I suspected maybe they had a new frame they're calling the SC3). The nice lady at NEF answered - "Yes, they can be used with the barrel accessory program, but just so you know, we haven't shipped any of those yet."