what cartridge are you reloading for? I just had this problem with .357 magnum and alliant 2400. I wanted to make top end loads for my ruger vaquero. After a week of checking things online and reading some manuals i found that with A2400 and a few other powders, magnum primers were fine to use; but the load had to be reduced...by MUCH MORE than 10% of maximum. I can't remember for sure but the manuals that used magnum primers for .357 were the new speer and nosler books....could be wrong about that.
Just to give you an idea of the powder difference between magnum and non magnum primers with that powder combo... one book listed a maximum charge of 2400 w/ a standard primer at 15.2. Another book listed the maximum charge of 2400 w/ a magnum primer to be 12.3 So if you have accesss to them check out a few different reloading manuals. Otherwise keep the mag primers and buy a box of regular primers as well. That to me would be cheaper than running 250 miles round trip.