I read somewhere (I think it was P. O. Ackley) that powders of a certain burn rate such as IMR 4350 perform better with magnum primers vs large rifle primers. As I have several rifles that I use 4350 for I'm going to compare the results of std vs magnum primers regarding velocity and group size.
This may have been more true in Ackley's time, both the powders and primers were different than now. In general I think primers have gotten hotter as more slower and ball powders were available. But this may not be across the board for all of them.
