I did not fire any of my bullets in the scene before we entered the attic. When I dropped my gun I felt stupid for not helping kill the zombies. Then Ben picked it up and gave it back to me with all the ammunition left in it.
Later Kenny asked me for if I had more bullets left, I gave him my gun and he fired two bullets. One definitely into Ben, and one I assume into himself.
Unless I spaced out during these scenes then I'm pretty sure that's what happened.
So Ben grabbing my gun, was a valuable act indeed...