If you feel you must start filing on your new ejector, I strongly suggest you copy the angle from the top of the stock ejector and don't bring the angle to a sharp point. You'll note the stock ejector has a slight flat at the point of contact with the cartridge head. Shortening the ejector to make sure that loaded rounds will eject cleanly may be necessary.

The important issue here is to get the ejectors point of contact with the casehead to be below the centerline of the case so that the case goes up and out. There used to be a famous name maker of these things that seemed to have failed to recognize that minor detail. The tip of his ejectors sloped the wrong way, driving the ejected empty into the side of the slide instead of out the port.