That's right, Manson crowning tool is based on Neway technology. I've developed it while working as an engineer for Neway Manufacturing, and offered it to my good friend Dave Manson. Dave, being an incredibly smart and professional fellow, liked it a lot, greatly assisted in fine tuning certain things and now manufactures and sells it under license agreement with Borka Tools. Neway cutter, when used as intented, can make, say, 2" dia. valve seat concentric to the valve bore within 0.001". Needless to say, for much smaller diameters of muzzle end of the barrels, which is typically under 1", concentricity is much higher, and close to 0.0005" or less. I did alter Neway carbide blades in a certain way, as standard blades will NOT work correctly for bores smaller than 0.75" dia. It is 10-20 times faster to do crown with use of this set up than with use of lathe, with equal or better accuracy results, and there is no need to disassemble rifle. It usually takes 2-4 minutes only, with use of electric power screwdriver, or 7-10 minutes with use of hand driver. Hand driver does have some advantage of allowing the user to crown with "fine feel", and can practically allow to get an extreme accuracy in the range of 0.0002"-0.0005" concentricty. For most applications, electric screwdriver with 50-175 rpm will do just fine. Serrated carbide blades will last for a very long time, as those were originally designed to do valve seats, which are typically much more difficult to cut than gun barrels.
Boris (Borka Tools)