You do come up with some odd thoughts. All of those guys with small bore double rifles probably should give up deer and antelope hunting with them since they aren't dangerous game.
I prefer to think of them as logical thoughts, Utah. "Odd" is a slightly perjorative term, at least it strikes me as such.
A double rifle is a special tool designed for a special application: quick, utterly reliable second shot with a heavy bullet at modest velocity. Thus two barrels, heavy gun, points like a shotgun, bold open sights, independent firing mechanisms. This formula is appropriate for dangerous game. It's the optimal choice. For any other type of hunting, the gun is heavier, not as accurate, is comparatively lacking in range, and is much more expensive than the alternatives eg bolt action or lever action.
Yes, there are some small caliber doubles around and people do enjoy using them on deer and boar etc, esp. in the brush, but that doesn't change the premise. Some of these folks are hunting dangerous game in their imaginations in any case. Good for them, I have done it myself.
In a converted vintage shotgun, I would NOT fire modern hot 45-70 loads, stick to the very mild BP equivalents. The old 45-70 looks like a big deal but in fact it's a very slow fairly weak ctg.
Now a purpose-built modern 45-70 double rifle is another proposition, if regulated for modern hot loads. I don't want to start a raging debate here (that kept AR aflame for about a year) but Cape Buffalo have fallen to this ctg. However, if you are going to get a purpose-built gun, get a 470 Nitro or a 450-400 or even a 375 Flanged and you will have a better gun that will fetch twice the resale value of the same gun in 45-70.
So back to the original question: I would save my money and buy a real double rifle. You can get a Valmet 9.3x74R (now branded FinnClassic) for about the same money. That gun will kill buffalo all day long. And for an extra $600 or so, you can add a set of shotgun bbls.
So Utah, what were the other thoughts that struck you as "odd"?>
