Almost 30 years ago, I took my 375 H&H to South Africa for a plains game hunt. I developed a load with the original Barnes X using their 250gn bullet. There was no data from Barnes back then, so I just started with 270gn data and looked for pressure signs while I worked up my load.
That ammo worked great for 8 plains game species from springbok to zebra. While I was in camp, I found out that there was a guy from Sydney hunting out of the same camp with a different PH. What are the odds of another Aussie being in the same camp while I was hunting? Back then especially it was pretty unlikely. We chatted most evenings and I got along with him fine.
At the end of the hunt, I gave all my unfired ammo to my PH and didnt think any more about it. 6-12 months later, I got a call from the other Aussie to say he had gone back for a cape buffalo hunt. He used a camp rifle in 375H&H and my PH gave him the 250gn Barnes X bullets I had left there. The PH wanted the guy to use the 250gn load as they were hunting a large herd and he was worried about over penetration with bunched up animals. They killed their buffalo with one shot using my ammo. The guy wanted to let me know and I was glad to hear about it.
Granted its a sample of one, but thought it was relevant to the OP.