30 yards is 90 feet. 50 yards is 150 feet.

Most of the critters you listed can do 30 to 40 mph easily.

If my math skills are still up to speed, an animal doing 30 mph can cover about 42 feet per second. At 30 yards, if you can reload and aim in 2 seconds, there is a slight chance. At 50 yards, you have not quite 4 seconds. Maybe enough.

For the 40 mph animal, they can cover about 56 feet a second. 30 yards being 90 feet gives you less than 2 seconds, and at 50 yards, you have just under 3 seconds.

All that said, this is why a double rifle exists. You have a second shot ready. While you need to fire it close to the timing of the first shot (the second barrel relies on a hot first barrel) I believe my Heym says within 8 seconds to have an accurate second shot.

Even with ejectors, I would bet that most of us could not reload and aim in less that 4 seconds. About te same amount of time to put your head between your legs and kiss your ass goodbye. Wounded dangerous game tends not to know it is dead until many seconds after a fatal shot is finally delivered.

You will probably see a lion, buff and elephant coming, but not a leopard. Lions and elephants, per the tales I have been told, can be deafening on a charge. And the Cape buff will move the ground between the two of you. So I've been told.

While a sidearm would be great, it is my understanding that they are not keen on handguns in Africa.