In the original pic with the pins in the gun they looked as if they had a sort of conical point to them. In the latest pic of the pins out they appear to simply be flat bottomed. I think that light reflection made them appear to come to a point in thar first pic. I would put a hemispherical radius on the ends of those pins. That flat end in the primer indent will actually tend to act as a bolt, while the rounded end will help to cam the pin back on opening.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra