Had great luck with my new SC made Model 70 300 WSM. Functioned and worked very well. Good trigger on it as well.
I can't tell if you need a lefty for your son, or you are a lefty only. Saying all that, Montana Rifle Company builds some very nice rifles these days. I agree on the 3.1" mag box of the M70 very 2.8 on a M700.. I liked having the extra room for longer bullets.
Good luck, sounds like you are setting your son up for success.
