I've found the Hornady .257 Rbts 100 g loads to yield acceptable accuracy. I would trust Hornady's expanding bullets, and use them second only to Sierra bullets in my rifle reloading. In some loads they actually outperform the Sierras, out of some rifles.
I was astonished at the accuracy of two completely disparate factory loadings of .257, though: the Federal Premium Nosler Partition 120g gave superb accuracy, and the cheapo Remington 100g SP (Round Nose, blunt bullet, flat base) gave surprisingly good accuracy at 100 yards (all touching a dime).