I'm new to reloading and have what might be a stupid question. I have searched for the question but haven't seen where anyone else has ask. Why the need for a head space gauge when the first stage on my re-loader resizes the brass back to factory standard. Is the gauge mostly for custom built rifles? I understand if I keep the brass separate for each rifle the brass will be form fitted to the chamber and then I could just trim as needed and just neck size them. I'm going to be reloading a lot of 223 for a factory rifle, Remington. The major reloading outfits like Ga Arms, they don't check every piece of brass after resizing do they? I've shot a few thousand of their rounds with no problem before deciding to start doing it myself. Thanks for the help in advance!