A co-worker/buddy of mine killed a nice 7.5 foot black bear over in Ketchikan a couple years ago. One shot kill, bear ran about 15 yards... He was using a .243Win.
30-30 is plenty, especially considering that it is likely a gun that you've been shooting with for quite some time and are comfortable with it = better chance of hitting what you're aiming for...
"To preserve liberty, it is essential that the whole body of the people always possess arms, and be taught alike, especially when young, how to use them." -Richard Henry Lee, Virginia delegate to the Continental Congress, initiator of the Declaration of Independence, and member of the first Senate, which passed the Bill of Rights.