Re: 357 magnum 158 gn fmj?
If the bullets are .357 or .358 inches in diameter, it don't matter that they were designed to be loaded in plastic cases. They'll work, loading into brass.
My only worry was you had Ranier or Berry bullets, which LOOK like FMJ, but are actually electroplated. The copper coating is not as thick as a jacket, and you can't push them as fast as you can a jacketed bullet.
But if they are, in fact, full metal jacketed, then yes, load 'em using 357 158 grain JHP or JSP data. You and they will be fine.
Meddle not in the affairs of dragons, for thou art crunchy, and taste good with catsup - George of Lod, Year of Our Lord 297
I always take precautions.
Beware the Evil Bullet Fairies.