Just cut a 410 barrel a couple weeks ago....watched several YouTube videos beforehand. Used a hacksaw with a fine tooth blade...32 tpi...and a hose clamp as a guide to get a straight cut. Finished with a file and emery paper. Found a small square gizmo at Home Depot that was perfect for measuring a square cut. Couple coats of cold blue and it looks pretty good for a first attempt. It was NOT a vent rib barrel.
I would not use any power tool as this is a slow precision job, unless you had access to a commercial band saw to do a professional cut. Saw a lot of die grinder buggered up cuts on yt.
Pretty much how I do it by hand. A buddy of mine has a full machine shop, I prefer to go over there when I have the time. Cut the barrel off in the band saw and face it square in the lathe.