Swift A Frames hands down, Nosler Partitions can sheer off too much weight and don’t hold expansion diameter as well as A Frames. A Frames are much better construction. And this is why PH’s recommend them. I’ve used A Frames in 375 and 458 calibers and was very pleased with the results.
Apparently you have little or no experience with the 9.3 286-grain Partition.
Over 20 years ago Nosler started redesigning some of the heavier, larger caliber Partitions to retain a higher percentage of their weight than the usual 65-70%. This was accomplished by modifications to the jacket, often placing the partition further forward.
The 286 9.3, however, didn't appear until after this was done to other Partitions, such as the 300-grain .375, so was designed to retain more weight from the get-go. I started using it in 2002, and the first animal taken was a big bull moose in northern British Columbia, shot at about 175 yards broadside, just behind the shoulder bones. The bull stumbled about 15 yards downhill before falling, in the process taking out several quaking aspens averaging 3-4" in diameter. The bullet was found under the hide on the far side, retaining 90.4% of its original weight.
Since then I've used the same bullet and load (which gets around 2500 fps) not only in North America but on more than one African safari. Have only recovered one other, from a blue wildebeest bull standing quartering toward me at around 200 yards I put the Partition in the big shoulder joint, and the bull staggered 20-25 yards before falling, obviously dead on its feet. The bullet was recovered at the rear of the rib-sage on the other side.
You apparently also didn't notice the post before yours, where Vlok (a hunter from South Africa) also has only recovered two 286 Partitions in his hunting, which retained 87.4% and 90.9% of their weight.
A-Frames are fine bullets, and I have used (and seen them used) considerably, but on average the 286-grain 9.3 does not penetrate as deeply as the 286-grain Partition, because it opens so widely--and average retained weight is about the same as the Partition. You may think the narrower mushroom of the Partition is a disadvantage, but the bullet still kills very quickly, and exits more of the time than the 286 A-Frame. In fact, on one of my safaris in Tanzania my hunting partner was so impressed with the way my 9.3x62 killed that he bought one himself upon returning home.
The other Partitions I've recovered from big game that retained 85-95% of their weight have been the 225-grain .338 (85.4%; from a huge bull musk ox, shot like the wildebeest through the near shoulder joint on a quartering-on shot), 300-grain .375 (an average of 88.2%, from buffalo); and a 400-grain .416 (95.2%) that angled from the rear of the left ribs on a Botswana Cape buffalo and ended up in the right shoulder. The 500-grain .458 is also constructed similarly; my hunting partner on a 2011 safari used it from a .458 Lott on Cape buffalo, but we don't know how much weight it retained because it ended up somewhere in the rear half of his bull--after a frontal shot that broke the spine under the bull's chin. We traced the bullet's path well into the guts, but couldn't find it.
