Depends on the brand. Some magnum primer just have thicker cups. Some have a little more brisance. Some have a LOT more brisance. The 45 ACP has a large margin of error and is not susceptible to the pressure spike problems of say a 40 S&W.
Long story short, I use magnum TulAmmo primers in 45 ACP and can't tell the difference...(I scored a case of 5000 cheap

)