That too, i am not ware what size the Two barrel is, i do think they are machined so the end nuts for the tensioning system are fine M14 thread, but not sure CUZ i have not take it apart to measure it up and make a drawing for what i would need to do myself or get others to do for me if i can source a cheap trustworthy person that know what the hell to do and how.
Taking a few .10 of a mm off, well off a thing that long and thin, not entirely strait forward on a lathe as the barrel would flex.
Personally as i do not have access to my grinding machine in my last job, well on a lathe i would use HS steel as you then have less cutting pressure that might deflect the barrel.
As a apprentice Machine worker i have turned some fairly long and thin / soft things, in one case going wayyyyyy outside of the box to be able to do it.
