Rick et al: Tested some bullets today including my much loved partitions. Interestingly the partitions penetrated no more than the 250 Speers largely due to tumbling.

When the bullet tumbles huge forces come against the side of the bullet including the back half and it is possible for the back core to squirt out.

Because the partition will only expand to a certain extent it remains fairly long. If the mushroom is out of balance or if it takes a force more to one side than the other it may lose it's gyroscopic stability in the target.

In this case the forces against the side of the jacket may cause the bullet to bend and lose it's rear core.

This is my hypothesis about how a partition can "fail".

I am having trouble attaching a picture but when I can I will post in the thread on .35 caliber bullet testing.