ORIGINAL: Triple Se7en
Now with technology going bonkers, new-age copper-clad Powerbelt HPshave already demonstrated that they'rea pretty tough hombre. As a matter of fact, more lack of expansion complaints have come from PowerbeltAerotip users than HP users. With magnum rifles/powders available, penetration is not even an issue here.
I will second that statement. Although I have not shot an Elk with a ML, the two times I shot Whitetails with the Aerotip Powerbelts, the bullet did not expand at all. There was a 1/2" entrance and exit hole. My friend uses the lead HP Powerbelts and the bullets flatten out to about 1 to 1-1/4 inches diameter. I have since switched to the TC Shockwave Sabots but these might kick more than you want for your son.