Here is my two cents:
I took my first moose with a 30-30 when I was 14. My first shot clipped his ear (I checked later), so after I realized I missed, I then realized that I was too excited. I calmed myself down and followed the routine (slow breathing, focus, focus!, etc.), then put a hole through his heart. Took us all night to pack it out to the truck, so between the kill and the work I was one proud fella when we pulled into the yard.
Hunted with that rifle for the next 6 years and never had a complaint with it. It has put a hole in a few or more hearts and has taken a few heads off rabbits and chickens.
One thing though, used a buddy's 30-30 on a running moose last winter and put three shots into his lungs at a little over 200 yards before he slowed down. By then it was time to reload, I did so and watched him as I knew that he wasn't stopping just to smell the flowers. He dropped and was dead before I got over to him, but I can't help but think that if it were a few months earlier (ie. mating season) and he was pi$$ed off and heading my way, I may have had a tussle on my hands if I couldn't have put him down with a neck shot.
Never had cause to shoot a bear or anything else of size, but moose and deer (usually!) fall just as quick with a well placed shot from a 30-30.
.... keep the change.