Dunno about 767's, but I've done nine (9) safaris thus far, eight (8) of them DG safaris. Have taken multiple elephants and buff, plus one (1) each leopard lion and rhino (the rhino was darted). Completed the Big Five in 2012. Going back to Africa for my 10th safari in June, 2018.

Killed the lion in Zim with a .416 Rigby shooting 400 grain Swift A Frames. Mistake! Bullet zipped through the lungs with no apparent expansion and the cat simply took off. Followup at night was, shall we say, exciting? Found him dead, bled out, with little internal damage. Way too much bullet for a cat, but that was the only soft I had brought. Great buff bullet, lousy cat bullet out of a .416, IMO.

Shot the leopard in 2012. Rifle was an early 50's Winchester Model 70 that started life as a .270. Sent it to Stuart Satterlee (Satterlee Arms), who turned it into a very nice .338 Winchester. Swaro Z6i with illuminated circle dot reticle. Craig Boddington recommended a 225 Partition as a good combo for leopard/PG. When the rifle was completed, Stuart brought it to Superior Ammunition (when they were still in South Dakota) and they made up (among other loads) a 225 Partition at 2,825 fps. Shot under one MOA. Brought that .338 and my .470 on my Namibian safari.

There was a rabies epidemic in the Kudu population when I arrived in Namibia. Plenty of meat on the ground, so the leopards were not coming to bait. The PH used a wounded warthog call and lo and behold, on the afternoon of the first day, a leopard appeared on top of a koppe at a lasered 191 yards. I shot him as he was looking around, broadside, through the lungs. He dropped where he stood and was DRT. Never even twitched.

I've only killed a grand total of two big cats, hardly a large sample size. But based on that, IMO, were I to do it again, for lion I would choose a .375 with a 270 grain Partition, CoreLokt or similar bullet. For leopard, a .30/06 with a 180 grain Partition or CoreLokt is about right. Actually, any good deer rifle (7-08, 7x57, .270, .30/06, .300, etceteras) with a "soft", frangible bullet would work well on a leopard IMO. But be advised that some countries require a minimum of a .375 for any DG, including leopard.

If the cat isn't DRT, I strongly recommend a good double with softs for the followup. I brought my .470 and 500 grain Woodleigh softs (as loaded by Norma), "just in case."