Do NOT use the cutoff wheel, use the hack saw. Your getting the barrel hot unnecessarily with the grinder, and leaving nasty crap in the bore.
Crowns are over rated. We've all seen the article, but I've done a lot of testing on my own. When I was a kid my dad built me a 96 Mauser in .250 savage for my first deer rifle. He made the stock short, but the barrel was too long, so he cut it down, filed the end square, set it up in a drill press and ran a 3/8" bit down the muzzle about 3/8" deep. It will hold 3/4" with 117g game kings whith me shooting, and slightly better with him shooting. One of the things I found detrimental was to sand on the muzzle. Your better off having a less than perect surface finish. And contrary to popular belief, with patience and know how, you can get the muzzle square with a file. Remember, a bastard file cuts one way, don't trag it backwards across the part, and clean it out often.
Of course, I have a lathe so I use it to crown my barrels, but you can do a good job without one.