Thread: Case prep issues

I just prepped up 50 once/twice fired cases, using the exact same process for all.
Being a newbie to reloading, I got into the habit of checking cases in my rifle before priming them. Well, out of the 50, 20 wont allow me to close the bolt, or at the very best, close it with too much effort.

I ran a couple of the dodgy shells back through the Hornady neck size die, but it made no difference.
What is going on ?