Are they talking about a lathe parting tool or an abrasive cut-off wheel like on a grinder or cut-off saw.
IllegalI cut em all with a portaband while in the lathe
That ^^^^^^, and there are lots of, shall I say, "not machinists" who are chambering barrels. A cut-off tool, a parting tool is not the best tool for a novice. Everything has to be right when you engage that cut-off to the work. Broughton has to cover their rear as they have no control over the methods, knowledge and experience of the person doing the work. If you can read a tape measure, the band saw is probably the best method to cut-off excess material without screwing up.My guess would be the pressure needed with a parting tool. And then not taking enough material off, for a nice clean crown. Just my .02.
Paul
Didn't we see that weekly here, on this "gunsmithing" board, a few years ago? Some trying to work too far away from the jaws, blade sticking out way too far from the tool holder and not square to the work and on center or just a thou or 2 above, and then on a lathe that is really too light and lacks the rigidity to run a cut-off? Then add in the taper on the barrel, itself.If the muzzle area has a taper to it, it will be hard to chuck it tight enough to use a cutoff tool safely. I have seen and heard some pretty good wrecks when guys were using a cutoff tool when they probably shouldn't.