Nor would I use one. If you think about it, especially if you shoot sabots, what is in your bore? You have powder residue, maybe some unburned powder, and sabot (plastic) residue. So if you are scrubbing across the rifling, you could easily get a buildup, no matter how minor, against the edges of the lands and grooves. Which will affect accuracy. Cleaning parallel to the rifling makes more sense to me anyway. That guy is just too lazy. (Or maybe he's not used to handling a big barrel like the rest of us in here)