You gotta tell us what you are using it for. For general across the board, a 375 h&h is a good compromise. 308-ish trajectory out past 4oo yards, but still enough for cape buffalo or elephant up close. Ammo not cheap but not crazy, and fairly available. Now if you are specifically hunting kodiak browns or plan on doing alot of Africa hunting, then you might want to get more specific and go 416 or 458, or hell 600 nitro. There is always a trade off though, as those big thumpers tend to be great up close, but don't fair as well for double duty as a 300 yard elk or moose gun. And as others have said, the 45-70 is quite competent in its own right. But just like a wrench, fitting the appropriate tool to its task is the bottom line.