I purchased a HK 93 bolt carrier off of GB last week. It came in the mail today, but something seems incorrect. The bolt carrier has a half circle protrusion, that sticks out of the right side, of the rear of the carrier, approx. 5/8 of an inch. So instead of the carrier being flat on the rear, it has this. I do not know what it is. I have compared it to any photos I could find of HK 93 bolt carriers,along with my own, and none I could see have this. I tried to attatch photos, I hope they are there. This was an expensive part, so I am really in need of some info. Thanks.