Does anybody know how hard it would be to sand and polish a blue barrel to stainless? Is getting a 'factory stainless' finish possible? Thanks in advance.
The steel under the bluing is not stainless. "Stainless" is not a finish, it's a type of metal, several types actually. You could certainly remove the bluing and get bare, shiny metal but it would rust in a hurry unless you protected it somehow. Like clear-coat.
You can get an appearance that is something like stainless (including the corrosion resistance) by having the barrel plated with hard chrome, electroless nickel, NP3 or something similar.
On a Glock, or any other barrel that's Tenifered or Melonited, you can remove the exterior finish without affecting the rust-preventative nature of the steel's treatment.