When I lived in Nunavut for a decade my wife and I took up to 10 caribou a year + being on friends hunts. Numbers pile up. Although caribou are pretty easy to kill I had the chance to look at wound channels from caliber 223 to .458 at all different velocity levels.

A friend had a 788 carbine in 243 that got about 2750fps with 100 grain factory ammo. Due to the reduced velocity that little bugger penetrated like crazy and killed very well. When we found the carbine 600 in 6mm we snapped it up. I loaded up some Barnes 115 grain RN Originals at the same 2750 fps. Again it penetrated like crazy and has been a good killer on everything we aimed it at in the NWT and Nunavut at up to 200 yards.

When Barnes discontinued the 115 grains I tested a bunch of bullets. The 100 grain Nosler partitions at 2900-3000fps penetrate just as well as the heavier Barnes and if anything kill stuff a bit faster. As a bonus the semi-spitzer version shoots into 3/4" groups.

It's not the best designated moose gun but it works if you are a calm game shot. Honestly the margin of error is no doubt less than say, my 358 Norma but even with the big Norma you better hit lung. Another bonus is that from my canoe I am less likely to be kicked out of the boat.

That being said if I had the money I'd buy your son a Savage ultralight in 260 or 6.5 Creedmore and he'd never need another gun in NA.