I used a Zip-Cut blade in my hand grinder ,works well ,patience is the key as well as preperation(a Zip-Cut is a thin metal cutting wheel ,but a Dremmel tool and cutoff wheel would also work)
I drew a line(Sharpie) around the circumference of the barrel using a strip of styrene plastic (thin cardboard or similar)and wrap it around where the cut was to be made.I then measured from the muzzle end to the line I marked at several points,to make sure the line was square and 90° (the barrel tapers from the breech to the muzzle)
I then cut very carefully watching for my line and staying on one side of it instead of splitting it.This will allow you to file or grind up to it in the final squaring up.I went slow and easy ,trying not to create too much heat...DO NOT RUSH !
I then used a file and squared up the muzzle.Then used alcohol to remove any felt pen marks.
NOTE: I also masked off the barrel to protect it from sparks etc.It may not be needed, but I like to be cautious.
I then chucked up a cone shaped grinding wheel in my Dremmel tool and removed any burrs inside the barrel.I finished up with some silicone carbide 300,400,600 grit W&D paper wrapped around some wood dowel.Take your time and check your progress.
I used a fine file to carfully chamfer the outside of the muzzle then finished up with the mentioned sandpaper.
Cold blue the raw metal (should not be much showing) and done.
It looks very good and professional.I replaced the bead with a Truglow snap on optic sight.
HTH
BB