Basically I just had a quick question, finishing another build and wanted to be sure on something. I understand when you assemble the new bbl to the new upper you are suppose to tighten/loosen 3 times to prepare the receiver threads. Is this necessary if you are just reassembling an old barrel to a used upper? Basically is the "tighten/loosen 3 times" mainly for new receivers or just to try help alignment? On some of my other rifles that have seen more than one barrel I just tighten the bbl nut up to spec.

You could do it to be cautious but, you'll probably be good if its used. I believe it is done to stretch the threads to help seat the barrel to the receiver. Do it, whats 45 extra seconds....and don't forget to at least grease the threads

Alright, thanks.