One reason many African PH's use heavy-for-caliber bullets is not as many "premium" bullets are available over there. Though that has been changing, ALL bullets are much higher-priced over there.
One of the PH's I've hunted with owns a big sporting goods store in Kimberley, South Africa. When I was there for a month in 2007, I visited the store several times. The shelves were dominated by cup-and-cores priced about like Nosler Partitions here, and the relatively few Nosler Partitions were at least twice the price they are here. Of course, most of the bullets sold were to local meat-hunters who often shoot a lot of animals, and heavy cup-and-cores work for them.
Today more premiums are becoming available and more PH's have discovered their virtues, partly through their clients using not just Partitions but TSX's and other bullets. But prices are still high, and the heavy-bullet mentality still exists.
