My 2 cents is 30-06 or larger for elk. Leave the shotgun for the birds, an animal as majestic as an elk deserves the respect of a high powered rifle that is very effecient at harvesting them(I' ll include muzzleloaders in this category for the sake of this topic). They are very strong and have earned the respect of a " elk rifle" not a " bird gun" .

If I had to pick between the 2 the shotgun at 20yds would be better than the 30-30 in a hold up. Please don' t bring a 30-30 elk hunting, its like bringing a knife to a gunfight.