That bevel on the bottom inside of the extractor tip is especially important, since as the slide pushes a round forward out of the magazine and levers it up into the chamber, the case rim is actually sliding up the face and into the extractor gap from below. A sharp extractor tip can dig into the brass at this point and cause a failure to go into battery. Bevel and smooth it and it goes like butter, but leave plenty of extractor above that to haul the brass back out after firing.