I would be proud as punch if he decided on a Marlin - in case you haven't figured it out yet, I have a bit of a soft spot for those! (The .35 Whelen built for me by the Fire was built on a Marlin X7 platform.)
Just to offer another option though, My son Timothy is just the opposite - a fairly small 12 year old. He's about 80 lbs. I had asked my friend who I get all my guns from to order him a Marlin X7Y (youth model - shorter stock) in 7MM-08. They were back-ordered though, so my friend took a chance and ordered a Mossberg Bantam youth in 7MM-08 instead. It has a 20" barrel, is quite accurate and Timothy absolutely loves it. It's his new favorite rifle. It came as a scoped combo, and has a spacer that can be put in the stock later to increase LOP as he grows. The scope is a 3-9X40 - a Bushnell I believe. My budget is significantly higher than the price of either the Marlin or the Mossberg, so we could consider a better optic, maybe a bipod - whatever you think James would like.
"Noone has a more intimate understanding of, or deeper appreciation for freedom than a soldier who has fought for it in a country where it does not exist."
