I used a 30-30 last year. I killed a 4 point w/ it. I shot it right in the heart. and the bullet didn't make it all the way through the deer. We found it in three peices. So I personally don't trust them w/ big bucks. But they are good guns.
I've never had a problem with them myself. We've shot several deer and hogs with them and I've never had one run more than 100 yards. We always shoot them in the heart and almost every one we shot the heart and lungs were just mush when we cleaned them. My grandfather used his to hunt in Colorado and he shot the biggest deer of the group. Everybody was telling him it didn't have enough power to kill anything large and he shot his right outsidethe campafter everybody left.