Tikka T3 / 270 Win / Burris 3-9x40 w/dots / Talley Lwts / Butler Creek Mtn. Sling (or 308. 7-08, 6.5 CM).
Can't see any wisdom starting a young guy with a 300 or 7mm Mag as an only rifle... those are something you get "in addition" to a standard chambering like the 270 when you've mastered it.
This^
If buying today for my adult sons, I would definitely start them off with something in the .270 class (7-08/6.5 CM) and let them buy something bigger if/when they decide they want it..... they will shoot better while not being abused by recoil.....