You have found gold. The 416 Partition has a very tiny front core and retains > 80% of its weight when losing the front core. They are not comparable to Partitions in smaller calibres, even 375. They penetrate very deep and I have more than one exit on buffalo body shots. Frankly to recall we have only found one bullet that was shot lengthwise by my wife into a sable at 200 yards from a 416 Rigby, entered on the arse and found in the neck.
When I hunted lion I switched to Woodleighs because my feeling it was too hard and expands too little for lion.
This year I shot a zebra facing obliquely on the shoulder and it exited the right buttock.
If I could only find any in South Africa I would buy all of them.