Ill vote for a .243, I used one when I was 12. I only weighed maybe 65-70 pounds. The recoil never bothered me. I have never shot a 7mm-08 so I cant say for sure but I wouldnt think it would be an issue. Here is a link to a recoil table for comparison. http://www.chuckhawks.com/recoil_table.htm

I'd say it really depends on what your son will be hunting. If its deer size game i would say go with a .243, great gun with very low recoil. If he's gonna be hunting elk, then i will say a minimum of a .270. still low recoil and with a well placed shot will drop an elk.

I'd say the 7/08 would be a perfect choice for a new hunter. There are reduced recoil loads available from Remington that have less recoil than a standard 100gr/.243 load and give you a larger diameter bullet of 140gr. And, as your son grows and becomes more tolerant of recoil the full power loads for the 7/08 are excellent for a wide array of hunting. I'd say a Remington Model Seven would be a great choice, but I'd also suggest you take a look at the Ruger M77 Compact as well.

Good Luck!

You may also think about a 308.  As said earlier you can put reduced recoil loads in it for the time being and when the time comes jump up to the big kid stuff.  You would gain lots of choices in bullets with this gun.  With reduced recoil loads your son probably wont really notice recoil.  Most 12 year olds at 70 pounds or 150 pounds are pretty resilient.  Make sure you get him out and let him shoot, shoot, and shoot some more.  The more he shoots the more comfortable with the gun he gets.  Also I have seen quite a few deer taken with a .243 and they never had a chance if you don't plan on having him shoot animals larger than deer.

i am in the same boat, good thread for me.

Though we haven't owned one before, I had heard great things about the 7MM-08 with good loads. Low recoil and able to bring down big game up to an elk, with proper bullet placement.

Purchased a Remington 700 SPS youth this year, one in .243 and one in 7mm-08.  My son and wife use the .243 for deer and the 7mm-08 for Elk. This model has a smal LOP, great butt pad and fits the little people well with no modifications. I handload so I worked loads for my son to get up to a hot loaded 140Gr Accubond for Elk.  He had no issues at all with a 100gr Speer for deer.  Took his first Mulie this year with the .243. I also have a nifty recoil calculator in Excel that helped with the recoil problem. Hope that helps  

  I have a 14 yr. old daughter and last year she had shot her first deer.  We are in the earn a buck unit so you have to shoot a doe before you can shoot a buck, this lets her shoot two deer. The first doe she killed was 200 yrds away and was taken with a .243 (DPMS AR-15) 75 grain Hornady.  She then shot her buck the following weekend with a 300 Rem. ultra. Mag. 180 grain Swift Scirocco. Both guns had muzzle brakes on them. 

  I am a firm believer in putting muzzle brakes on high powered rifles, it dramatically cuts recoil, I even have one on a 22-250 (prairie doggn'). If your to scared to pull the trigger your going to flinch and miss your target.  In my opinion, if you have youngsters and they want to shoot bigger cal. at bigger game, put on a muzzle brake.

I think any of the guns mentioned would be a good gun for a child, for deer sized game. Whatever caliber you choose, make sure to take him to the range and let him shoot.

Make sure he has good hearing protection on, IMO that loud bang is what really rattles/scares the younger shooters. Ear plugs and muffs wont hurt to start with. As far as the felt recoil, you can always get reduced loads as mentioned in a previous post, or add a recoil pad. 

Gotta disagree with hunterkirk on the breaks.  Stick one on the end of the barrel, have junior pop a cap without hearing protection (by design-stupid or by accident-human nature) and he/she will flinch for life.  A properly fitted and sized rifle is the best way to control recoil along with good training and practice.

Like the 7-08 option; went that way with my daughter - a Weatherby Youth model with a downsized stock just right for her 5'2"'s.

And a muzzlebreak on a .22 centerfire?  Seems kinda like giving a condom to a priest.