There are some answers to your questions, but I'd like one answered for me! What make is the 45-70 and is it a double rifle?
The fact is the 45-70 cartridge is not legal strictly speaking. Though it is OK on the diameter department the cartridge simply doesn't develope enough muzzle energy to qualify for things like Cape Buffalo, or larger dangerous game. I would be reluctant to use it on African lion as well, and that only leaves Leopard of the big five. That is not to say you wouldn't be allowed to use the rifle on those animals simply because most game scouts are not well up on ballistics, and look only at the bullet size. The one who needs to know is you, because if something happens, and someone in the safari party is hurt, or killed by a wounded member of the big five, and the real athorities find you were useing an illegal caliber, and can find nothing else to blame, you, and your rifle are the most likely suspects!
The big hole in the muzzle doesn't necessarily make a rifle a "STOPPER", and though I love the old 45-70, and own, and have owned several rifles so chambered. I wouldn't take on a Cape Buffalo, under all conditions, with nothing but a 45-70, especially with a 325 Gr FTX. The lightest bullet I'd use would be a 480 gr Woodliegh soft, and solid, and loaded up to the hot Ruger No1 loads.
As far as the plains game in Africa the old Indian killer will show it's muscle! If I were going to Africa and wanted to blood the rifle there, then I would take it, and do just that. If there will be any of the big five involved on the menu, then I would take another rifle as well for that, minimum 375 H&H with 300 gr bullets both soft and solids !
I know the 45-70 looks like a big bore cartridge to folks that have never been exposed to real big bores, but frankly it just isn't that lethal, on anything tougher than say a good broadside shot on moose, and a 30-06 is more than enough for that. The rule is basically just under 5000 pound feet of ME to be legal.
