The front sight unit is made from extruded aluminium so I would imagine as Troubledshooter says, a little heat should do it. It's likely that this would have been either a low interference press fit or heated before being assembled to the barrel. My monies on the press fit as it would have been far easier to control.
Please let us know how you get on if attempting this .. I have had a project in mind re a longer barrel similar to that tried many years ago on a post war senior. ( Ref Webley Air Pistols/Gordon Bruce/page91 ) although I would probably try it on a Hurricane.