[Styrak]

Well I solved my own problem. I used a small sanding drum with a fine grit slip on paper, and went at the end of the barrel at an angle and pressed the sander and barrel together while twisting the barrel around with the hand holding the barrel. So it does have a proper crown now (and as you said m#, it doesn't really matter the angle.)

Seems very smooth, even fixed my first botched job. Only a shooting test will tell if it's completely deburred.