Im fixing to turn 18 and on my birthday i want to go buy a new rifle that would be good for whitetail. I already own a 7mm mag, 30-06, 30-30, .243, sks, and a .270 win. I don't need a caliber as big as the .300 because the average shot is no more than 50yrds, however at times it could be up to 400 yards. What do yall believe would be a good caliber to purchase?