I used a .375 Ruger on my Kamchatka brown bear and have only praise for the cartridge. The first shot was taken at less than 20 paces. The 30-06 length action is very handy if you have put lead in the air in a hurry. I used a .338 Winchester magnum with a 250 grain slug on my lion and had no problems @ 27 paces. If I was going after leopard I would use a 30-06 with a good 180 grain deer bullet loaded as fast as I could safely go. No mono metal or tough bonded bullets. They may not expand on a soft target such as a leopard even at close range. A Nosler Partition would be as tough as I would go. I would probably go with a Speer Grand Slam or even a flat based Hornady Interlock as I believe them to be superior to the Partition as deer bullets.