I don't mean no disrespect(I'm plannin' on comin' there one day!),but I hear your deer don't get that big in body,so why not look at a .243/.260 Rem or 7mm-08 for him.All are adequate for deer,and are easy on the shoulder as well.Just remember though,that recoil is influenced by gun design,weight and action type(semi auto's use up some of the recoil to cycle the action),as much as by the caliber of the rifle.Hope you find something for him.....maybe try asking around(friends/fellow hunters or at your local shop) and see if anyone will let him try different calibers/rifles to decide before buying.....good luck to you and your son!