I don't know anything about muzzleloaders, but this thread and the other on elephant hunting with a muzzleloader caught my interest. The general consensus here appears to be that it is inadequate and unsafe. I know someone that pretty much exclusively hunts with muzzleloaders. He has a number of them and I am not sure which he used for what animal. I know he has a 6 bore that i handled one time and it wasnt something I would like to lug around all day. He is a very accomplished hunter and has many animals in the SCI top ten (for muzzle loaders). He has over 500 animals in his trophy room, so that should give you an idea.
Also Jim Shockey is a big muzzle loader hunter. You can see Jim's animals in the SCI Muzzleloader top 10 records also. An incentive for those trying to get top 10 or 20 animals is that there are not many muzzleloader hunters, so even a bronze or silver may make it to the top 10 for that category. Although, I am not saying that is Jim's intent for hunting with muzzleloaders. The SCI top 10 list is publicly published, so you can just do a google search for it and don't have to be a member or have subscription.
The problem most will run into is that you cannot take the powder on most commercial flights, or at least it's not easy. But to say that muzzleloaders are inadequate in general I feel is incorrect. I think it all depends on the equipment. There are many that have used them before in Africa and some that still do.
Just my 2 cents and as stated, I don't know anything about muzzleloaders. Just know people that have hunted with them a lot in Africa. I personally would have the PH ready to back me up if using muzzleloaders. Not sure how others do it.