Did the standard mods (AR, NF spring, lock removal) and then had a thought.
"I wonder if that 17/32nd brass over there fits inside the barrel"
So I tried it and what do you know, it fits.
First, cut around an inch of the brass, and hammer it in until it if flush with the half pipe of the original barrel. Now grab your dremel and cut the brass to fit and look the exact same as the half pipe. Sand it clean and you done. This tightens the hold on darts allow more pressure to build up which adds range.
Works with streamlines and some 13mm FBR (sorry informer, not yours )