Just got a new batch of 257 weatherby brass, I am shocked by the difference in weight. I am retiring my old 50 pieces for a new 50. I was hoping to be able to make the transition pretty easy instead of a new full work up. But that isn't the case. My old lot is 30 grains heavier than the new brass. I was very surprised at the difference, that could be why my rifle was using loads 4-5 grains below Berger data and exceeding their speeds with the 133.