The 30-30 basically has the same (almost exact) balistic characteristics as the 7.62x39MM round. THe only exception is that the .30-30 has either a 150 or 170grain bullet, while the other has a 123gr. bullet. (There are some 150grainers for reloaders with the 7.62).

With that said, the .30-30 is basically a good 150yard or closer deer round. Yeah, a .22 rimfire technically could kill an elephant, but what a torturous and dangerous task that would be.

Stick with an '06 like Blain said earlier for anything bigger than a deer in N/America.

As for the .223, using a .55gr or 62 grain soft point works wonders on a deer with the right shot placement. I personally use a little bigger gun like the .243.

Just my opinion.