The front core in all Partitions is a very soft lead alloy. It's not only softer than the lead alloy used in the rear core, but soft than the alloy used by just about any manufacturer of cup-and-core bullets.
This is why the front end of Partitions opens up so easily--and why it kills so well, despite the abudandance of hunters who think a Partition has "failed" when the front core is gone. The fragmenting does more interior damage, and that's exactly the way John Nosler designed it to work.
Just as often, however, we also run into hunters who think a Partition didn't open because the exit hole is only slightly larger than the entrance hole. This is caused by the same thing: The front core disintegrating, and the thin jacket around it folding back alongside the rear 2/3 of the bullet.
In fact, it is commonly assumed that a small exit hole with ANY bullet means it didn't expand. Almost always, field-dressing the animal and looking at the damage to the chest cavity will reveal that the bullet really did expand.
I remember a nice mule deer buck I killed one evening in Wyoming with a 115 Partition from a .257 Roberts. It went down within a few yards, but only had a "caliber-size" exit hole on the far side of the chest. Yet when I opened up the buck the chest was full of blood soup and a number of separate pieces of lung.
The truth is that almost any expanding bullet will be fully open by the time it penetrates its own length, whether the bullet is a Sierra GameKing or a Barnes TSX. The only bullet that I know of that delays opening is the Berger VLD, which normally goes in a couple inches before disintegtrating. All the others expand quickly--especially the Nosler Partition with its soft front core.
