bsa1917,
These days Nosler continues to tweak any of their bullets if they see the need.
The 300-grain .375 is one of the Partitions they moved the partition forward on a number of years ago. If you recover one, they typically retain 85-90% of their weight. The only two I've recovered (after shooting quite a few into various African animals, and a couple in North America as well) both retained around 88%, give or take a few tenths of a grain.
Since then Nosler tells me they now use a harder rear core in the 300 .375's, though as I recall the change had more to so with accuracy in some .375-caliber rifles than anything else. I haven't used any of those on game yet, however.
