Thats alot of great advice, I forgot to take into consideration you may not be as big a 15 year old as I was . when I was 15 I stood 6' 4" tall and weighed 260 lbs. I Began shooting a 300 win mag when I was 13. One caliber mentioned the 308 win is an excellent caliber also one of my favorites. Its hunting capabilities are endless, I use one for elk when hunting in wooded terrain with a 180 grain nosler partitions where shots generally are no further then 100 yards. In my first post I was assuming you might be hunting in the west where shots could possibly be out to 400 yards, even to 400 yards with good shot placement you dont neccisarily need a magnum, but any of the other calibers mentioned in other posts will do the trick except for the 30-30 it would be quite iffy for shots over 150 yards. good luck