I have purchased new brass a few times and it just dawned on me that I did not resize it because I did not need to remove the primer. Should new brass be sized? I just resized 200 new 9mm cases. Did I waste my time? I figured better safe than sorry. I have fired about 100 .45 rounds that were not resized, and they seemed fine. I searched my reloading book and so far haven't found anything about resizing new brass. Seems there is always something new to learn about reloading.