Re: First time shoulder bumper
The thing is, as brass is sized and re-sized over and over it work hardens and gets a certain amount of Spring Back. So both neck tension, and the shoulder both become inconsistent over time. This of course is very destructive to accuracy, but far too few people ever realize it.
So it is really about taking care of "that end of the brass" as it were. When you Neck Anneal, you also anneal that part of the shoulder. The shoulder is the lesser of the two really, but it CAN be important. Hence Shoulder bumping. If you choose to shoulder bump, then you should do it every time. Other wise you are introducing an inconsistency into your reloading process. What fj40mojo said is dead on. Thing is, one to two thousandths is all you want! Less really is more, as he said, you want to avoid excessive Head Space issues introduced my excessive shoulder bump.
Have a good one,