At 7mm-08 velocities that bullet should behave pretty well. Modern ballistic tips are tougher than some people give them credit for. I've recovered 165 grain ballistic tips and accubonds fired from 308s and '06s from several critters, weight retention and expansion are very similar, only way to tell them apart is the accubonds have more lead stuck to the jacket. I've never gotten a ballistic tip to explode on an animal, even at extemely short range in a 240 weatherby. I'll be running 150 BTs in my 7-08 on a cow hunt this year, can't imagine it'll be a problem. If your son is recoil sensitive the 120 BT in 7mm is a tough little bastard for it's weight.