Some individual’s skill level limits them to ranges less than 200yards. Their rifle may be capable of much greater rangers but this is where they practice so this is there “Comfort zone”. Some people only feel comfortable shooting a 400lb wild boar with a 300 Winchester magnum at 150 yards. Other people are perfectly comfortable taking the same wild boar with a 7’ spear. Some people hunt coastal brown bears with 375 H&H magnums others with a bow and arrow.
The 45/70 has taken Grizzly, Lion, Cape buffalo and many other animals in Single shot and lever action rifles. Its performance has stood the test of time.
Randy Garrett offers (http://www.garrettcartridges.com/) 45-70 ammo, which has been used successfully on African dangerous game. The Sharps is still a world-class rifle that is more than capable. I have no experience hunting in Africa but I have been shooting the 45-70 for 20 some odd years and I do own a Sharps. If you do decide on a sharps the best ones come from Montana