Works fine on a modern gun that you load from the rear, but not an easy way to do a muzzleloader. If you plan to load
it from the front, you will need a lot more than what you can do with a brass screw and lapping compound.....Don
Of course, Don is absolutely correct about a muzzleloader barrel.
I'm not so sure the method shown in the video is that good even for a breechloader.
Barrel crowning really should be broken down into two operations, i.e. 1. barrel facing and 2. Bore crowning
The face of the barrel can be of various shapes or styles and work equally well as long as they are as uniform to the bore as possible. We tried a host of different style barrel faces for the Model 40A1 Sniper Rifle when we developed it and kept working for years on improving it, and found what many bench rest folks had always said that this was indeed true. Many earlier .22's had a sort of mounded shape barrel face to protect the bore crown from damage should the rifle be dropped on its muzzle.
A flat muzzle face (as shown in the video) won't protect the bore crown as much, but it will work fine for accuracy as long as the flat crown is perpendicular to the bore. But that's the problem, we don't know from the video if the muzzle face was perpendicular to the bore after filing and sanding. If the filed/sanded muzzle face is more off center than the old muzzle face, the rifle could/should be less accurate than it was before he filed it.
I have to admit I shuddered a bit when I looked at the bore crown in the video when he was done. It's quite easy to see after the way he used the brass screw and lapping compound, that the bore crown is not uniform and therefore not going to be as accurate as a uniform bore crown made by a lathe or even a good piloted bore crowning tool.
I'm always a little suspicious of claims of improving accracy when testing is not done. If that .22 rifle in the video only shot a 6 inch group at 50 yards and can shoot a 5 3/4" group after the way the barrel was crowned in the video, then accuracy was indeed improved - but how much value is that? Why not do it correctly and have the barrel shoot as good as it can?