I am not sure what that part of the barrel is that looks like a pad of some kind, but it shouldn't be there
A small note: The slide lockback position on those guns is not the dismount position; the dismount position is with the front for the slide about 1mm in front of the frame. The barrel can then be turned clockwise (as viewed from the front) and the slide can be removed. Unlike many similar guns, the barrel cannot be removed from the slide by pulling forward; with the slide upside down, it is tipped up at the back and pulled out backwards.