You can make a barrel from a blank, but you are not supposed to make a barrel shorter if it was one already.
Dumb and painful, but them's the rules in place.
Since you have machining capability, buy a blank and start from there. Cooey barrels are pressed and/or pinned in place. Not rocket surgery to get apart and re-install a NEW barrel. Folks like Mysticplayer, Obtunded, Jaunvaldez, or several others can sell you a suitable blank. Dlask Arms, and Bits of Pieces are two manufacturers that get mentioned a lot.
As a cover with the lad, I'd suggest sticking to the "there's a problem and I have to take the barrel off to fix it" line. Not untrue.
I'd like to see pictures!
Cheers
Trev