I have no dog in the Kevin Robertson discussion (other than running some of his articles in Successful hunter), but I don't think the comparison of the 9.3 and .30-06 loads demonstrates much.
First, different bullets sre used. The TSX is probably the deepest penetrating expanding bullet on the market. The North Fork, good bullet that it is, is not. Mike Brady told me himself that he designed it to expand and penetrate somewhere between the Woodleigh and the TSX. (The Woodleigh is one of the widest-expanding bullets made.) This is exactly where the North Fork showed up in penetration tests, both by Mike and others, before he distcontinued making it for general sale.
Second, there is not as vast a difference in penetration in different calibers as many people think, when bullets of the same approximate construction and sectional density are used. This is not exactly new information. Finn Aagaard did a test many years ago, using wet newsprint, and while several bullets were used, most were Nosler Partitions, as they were the most commonly available "premium" at the time. Cartridges included the .30-06, .300 Winchester Magnum. .338, .375 and .458 (if I remember correctly), though obviously the .458 could not be tested with Partitions back then. The main point is that ALL the heavier Partitions (200 .30, 250 .338, 300 .375) penetrated within 10% of each other, to 20-22" in the wet paper, no matter the cartridge. Instead of overall deeper penetration, the advantage of a heavier bullet is in its abilty to penetrate tougher stuff (whether bone or muscle) and still remain on course and get inside.
Third, the ability to penetrate hide is quite variable. I have seen bison chests penetrated completely by a 130-grain TSX from a .270, and 300-grain .375 Nosler Partitions stopped under the hide (even though retained weight was 88%).
I have shot quite a few animals with both the 9.3x62 and .375 H&H. No, the 9.3x62 isn't a .375, but it comes darn close, especially when handloaded with modern powders. In a 24" barrel it is no great trick to get a 286-grain bullet to 2500 fps or so at 60,000 psi. This is extremely close to the standard .375 300-grain factory load at 2530 fps. Of course, the .375 can also be steamed up a little over factiory pressures, but not nearly as much as the 9.3x62, because the 9.3's factory loads operate at much lower pressure.
I do know quite a few other hunters other than Kevin who have used the 9.3x62 (and 9.3x74R) on not just Cape buffalo but elephant, and to a man they regard the 9.3's just as highly as the .375. One of these is a PH in Tanzania who uses it (illegally) there, and with standard African factory loads. The 9.3's are not, however, as generally legal as the .375 in various African countries.
