My experience is that crimp only does so much good and I have the belief that magnum primers just don't help with #2400. I would look up some Federal 100s and increase your charge. Most .357 shooters I know have settled on a charge somewhere between 13.0 and 15.0 grains. Charges below 13.0 grains always seem to give high extreme spreads. I am always looking for an extreme spread of less than 50 FPS in my magnum revolver rounds - less, if I can get it.