This may put into perspective how under powered the 30-30 is for brown bears. I worked with a guy that shot a 550 lbs black bear 2 times in the chest with a 30-30, his hunting partner heard the shots and shot the bear with his 06 killing it. They were disputing who actually killed the bear. When they skinned the bear both 30-30 round were found mushroomed against the bears chest but did not penetrate into the vitals. Now Iconcide that had the 30-30 shot the bear behind the shoulder it probably would had done the job, but a backup gun will by definition require a frontal chest shot on a charging bear and I just dont thinkeither roundcan do what you are asking it to do. If you cannot afford or borrow a 12 gauge I would rather have a sharp spear or better yet a bayonett on on the rifle because you will need it.