Folks, I tried to search for the answer to my question, but could not find the data and/or can't remember where I read it, so I thought I would throw it out here. At what point do most decide to go with magnum primers vs standard primers in rifles? I usually follow the recommendations of the manuals, but in some combinations, it's not that obvious. As a rule, I have always assumed that over 70 gns and slower burning powders, like RL22, (I guess I could say when using a powder with a burning rate factor of less than 0.40) it's time to go bump it up to magnum primers. Does anyone else have a better source than my simplified rule of thumb?