It is also possible that the core material might be a different hardness (though not necessarily the case here with Berger Hunting VLDs).
Target bullets usually use very soft (nearly pure) lead cores. This forms easier, allowing for more accurate production of the bullet.
Big game hunting bullets often harden the lead by adding a bit of antimony or other alloying materials, so that the bullet is stronger and more suitable to a controlled expansion design. Varmint bullets often use soft lead cores just like target bullets.