I stopped in my local gun shop on sat to inquire about supplies. No powder but he had a box of primers. When he handed it to me I noticed they were magnum primers (cci 550's). I looked puzzled and he quickly said "these are fine, no problem, don't worry use 'em just like the 500's I promise you will have no problems at all". I bought them. And now am having second thoughts. I'd like some opinions from you experts. Should I use them the same as the 500's? Or not?