The only time I've done such a thing was when there was a problem. Probably every other cheapo airgun that I've had suffered a burr or some such imperfection in the crown area. All were resolved by the brass domed screw head trick, just twirling it between my fingers while rotating the barrel (the whole gun) so that there is no set orientation of the barrel.
A Diana 250 I have (cheap springer) wasn't as accurate as I would expect, and I noticed the muzzle end felt a little funny when I'd push a pellet through. Not really a choke but gritty. So I lopped 2 inches off the barrel, thinking that I certainly couldn't make it worse. I just marked with a pen and used the hacksaw, which didn't even follow the pen marks. Then I filed away to even it out, eyeballing the "flushness" of the new muzzle, and finished with fine sandpaper. It ended up more rounded than squared off. Then I hand twirled drill bits at the bore opening to cut in a little crown, just a couple millimeters. I turned the barrel around while I twirled so that the angle or curve or blunderbuss or whatever the new shape was of the crown, was at least similar all the way around. Then I did the domed screw trick but with fine sandpaper over the screw head to remove any burrs, and cleaned the barrel. In the end it shot a lot better, so I was happy, but under a magnifier it looks like... nothing because the plastic front sight covers the scars.
But I wouldn't do such a thing to a perfectly good crown from the factory.