About Trumpet: Widen the Throat of a Mouthpiece

I widen the throat of a Bach 5C trumpet mouthpiece which has a throat # 27 (144" / 3.66mm in diameter) by drilling into it with a 5/32" drill bit (.156" / 3.96mm, between throat numbers 22 and 23). I also did it on a Bach 10.5C. (The drilling part in the video is actually the 10.5C one since I've already done the 5C one.) I also applied the reverse rotation on the drill.