When I first started working loads for the 454 Casull, I used Remington SMRP they worked fine in warm weather, but using Max loads and using ball powders in cold weather, I thought I would go to the Mag primer for better burn, worked very well no problems and powders burnt very clean, noticed the Rem SMRP did to burn as clean either. FPS does go up so In warm weather decrease loads if worked up in the cold, I just play it safe. Aim small hit small. RAMbo.