Greetings!! I have a super 14 bull barrel, and it's at this time being permanetly extended to 16.5 inches. It's a 7mm tcu, I think it would make a great youth gun when completed. My ? is which forarm will I need to order, since its a 14inch barrel, but i will need a longer one for rifle configuration. Will a regular 16inch forearm fit, same screw spacing,channel size, and such? Thank YOU !!