I use a Lyman flashhole uniforming tool. It probably makes zero difference in the real world, but when the winters get long reloading OCD kicks in.
I use this tool also, doubt it makes any difference in the shooting I do, but it only takes a second.
Yesterday, while randomly picking up and inspecting once fired WW brass, I found part of the breakout from the flashhole being punched out folded back over the flashhole and obscuring part of it. Doesn't happen often but I have seen that in the past. And that's the biggest reason I uniform flashholes, especially for brass that has the hole punched.
My Lapua brass on the other hand, I don't think a guy can improve on the flashholes......
