I have read that it is easier and more accurate, to file the lands to just below the bottom of the grooves, then file the grooves out about .005 or .006" to make the muzzle appear to have a squared muzzle.
If filing a muzzle, that is how I would do it, however the radiused crown is so easy in comparison and comes out perfectly centered, each and every time.
Incidentally, LB had a .40 that had a coned muzzle. With that cone, he still used a short starter to load a .020|" or so patch with a .395" ball - the starter was needed, gents. He ran out of .395's, so I gave him a bunch of .400's. These, he found almost impossible to load with the same patch, which was thinner than the patches I used in my .398" Goodoien barrel with the same .400" balls.
I thought he must be pulling my leg- until I loaded his rifle with the .400's and my patches. They were exceptionally difficult to get started then down.
Reason?
The gentle taper of the cone increases friction by spreading it over more of the ball's surface. Corbin, the bullet swage and drawing die manufacturer explained this quite well. A short radius is cut into the die mouth, which forms the bullet and jacket much easier than a long taper due to the increased friction of the long taper.
This is why the radiused taper works better than a cone. Too - the shorter the crown, the close the muzzle is to a square cut, which is MUCH more accurate than any sort of crown. The deeper or longer the crown, the less accurate it will be.
THIS is THE reason that false muzzles were invented for accuracy rifles, so the actual muzzle surface could be clean and sharp for the perfect delivery of the bullet and/or patched round balls in RB bench guns.
A shorter muzzle crown automatically is more accurate than any coned muzzle, in other words, the coned muzzle has the potential to be the least accurate.
I measured the crown depth on several of my rifles and they ran from .035" to .050" - less than 1/16" inch, which is about .0625". This is a long way from 1" or 1 1/2"- with easier loading and much better accuracy - POTENTIAL.