Not sure if this has been asked before. What is the point at which some one should switch from standard to magnum primers. Does it go by charge weight,burn rate of the powder or temp most shooting will be done. Part of the reason I am asking is I am working up a load for my 280 Rem. I am using slow powders in the burn rate of Rl 25 to push the 168 VLD Hunting bullet. These powders max around 60 grains of powder give or take. I started load work up with the Fed 210M primers but I am wondering if the 215 might be a better choice. Seeking the help of the experts here.