It makes the hole exactly the same size every time depending on carriage position. and puts the hole dead center in the baffle. Just like using a boring bar but much faster and cleaner and no pilot hole required. I dont run 9mm any over .400" bore or end cap exit and have never had a baffle strike cut this way. . Just plunge cut and adjust for diameter then lock the cross slides. You can drill out 10 baffles in 5 minutes start to finish exactly the same. Drill bits walk and egg the hole.Not sure why he chose to use a die grinder and end mill to make the hole.