This is what Remington has to say about the subject:

Thank you for your inquiry. Each Core-Lokt bullet is designed to
mushroom – expand properly, over the range of velocities likely to occur in
the field with the cartridge that it’s used in. This means tuning the
jacket and even the hardness of the core in some cases. We actually
have bullets of different configurations for different cartridges in the
same caliber. We have a 140 grain bullet for the 264 and a different
140 for the 260. Not all of these are sold as component bullets, which
may be part of the confusion. Even though the price of copper has
nearly doubled over the past two years, we haven’t thinned out the jackets.