I have to laugh at some of these posts, hacksaws and pipe cutters.... plumbers tools not gun plumbing tools.
My personal opinion is that a crown cut properly on a lathe = much better then a factor crown.
(1) center your barrel up using range or indicating rods. in a 4 jaw chuck w/isolating material (Copper / brass) and with a tail spider.
(2) Cut the barrel with a cut off tool and profile the muzzle to desired angle or design.
(3) single point cut the crown from in to out leaving a sharp but clean edge
(4) take a q-tip and drag it out of the barrel past the departure cut and if it leaves threads go back to step (3) until it is sharp, and clean
(5) fire lap it with a few rounds and check it.
(6) SOME people and some smiths like to take a marble, epoxy a drive stick on it and then use some grinding compound to lap the sharp edges, since most of my rifles have some sort of flash or muzzle bling I don't care, the chance of the crown being damaged is slight.
You can buy a jig from manson reamers that indicates on your barrel and then recuts the crown. Fancy tool for a one job application, but it is cheaper then buying a lathe and the tooling.
https://mansonreamers.files.wordpress.com/2015/06/small-file-july-2015-catalog.pdf page 15
cheers,