darn, well thanks for your input, and yes this is the link to the aluminum tubing
http://www.mcmaster.com/#89965K371 , and i guess it's not rated for 1400, but rather maximum of 1400 psi.
with my interpretation of the manual this would however be legal if I were to buy an actual pneumatic tube as the launch tube and only partially assemble it as then I would be assembling the pneumatic components using the pre-existing threads in compliance with R76 C.
"assembling and connecting pneumatic COMPONENTS using the pre-existing
threads, mounting brackets, quick-connect fittings, etc.,"