I once bought a case of .223 Rem UMC FMJ and it didn't shoot great in my bolt-action. One day, I wanted some varmint ammo, so pulled the bullets on some UMC and replaced them with Sierra 55 grain spritzers and shot them for groups. They shot about 3/4" at 100 yards, while the UMC bullets in the same cases and powder charge shot only 1 1/2".
People are like rifles. Some are tried and true, having great eyes, personality, and fun to be with. Others never seem to hit the mark with you. Still others go off half-cocked. Still, it's nice to know most of them.