I'd send it to Shaun at I.S.P mate.
http://www.isp-airrifles.co.uk/
He is going to machine a HW80 barrel for me to fit my Mk1 Rapid, and thier bluing is first class, my Rapid has a MFR style barrel shroud/silencer, made by I.S.P, and the finish is like black pearl !
Steve.