You will know when you hit the pure white wood of hickory. If you are guessing, then you haven't hit it. Once the bark is off, you will have the soft bark under it. It will be kinda figured to the bark that was on it. Then the soft layer under that inner bark. If you leave it for a few weeks wet, this layer will turn brown.
I have had luck leaving this on but only drawknifing thru here and there and it looks camoflagued when it browns up. You can then use some heavy sandpaper to get it off if you desire. But makes good camo.
I cut down a hickory in early Oct, thinking it would be wet enough for the bark to fall off. I have about 12 staves from it. And basically the bark was on pretty tight. I am trying to remove the bark now, and holy cow, I am throwing sparks gettting it off.
I see folks violating a whole bunch on hickory, and coming out ok.