If the tubes you make are well fitted with no (Minimum!) clearance, the 1518 would likely work.
Remember, they will be supported by the original barrel.
Past 10 inches, pressure is low.
I have made short (2 3/4) inch long) 16 to 20 adapters from similar, and lock-tited in place.
I have had no problem.
My advice worth what you paid!


Dumb, but learning...Prof Em, BSc(ME), CAE (FYI)