no need to remove the barrel, just heat it all up evenly and twist it off. I've not see one with a grub srew yet, but maybe it's a thing on newer rifles ?
But if this is a new rifle, I would have AA sort it, as you might slightly discolour the bluing. but it's generally fine, just let the heat soak in rather than trying to rush. Also be sure to remove the plenum if you have one, as the plastic will melt.
Always looking for any cheap, interesting, knackered "project" guns. But not lathes. I have too many lathes. Thanks, JB.