So I shot 8 rounds through it this afternoon. One round in the mag each time, using two different mags, just to make sure it's not a mag issue.
Every shot, the slide came back just enough to half cock the hammer and no more. It did not come back far enough to lock open on an empty round.
The brass had no odd marks at all. The rim is perfect all the way around.
This is what the hammer looked like after every shot.