while not a 7x30 waters, I have hunted with the 7x30 imp in a t/c contender carbine. took deer with both the older 120 gr nosler bt (red & green box) and the newer 120 gr. noslers. Out of my 24" barrel using 36.5 grs of 4064, the 120's are doing 2800 fps.
shot was at 75yds full frontal chest...
important that rifle fits your son as cheek height and to some extent length of pull will change between standing, kneeling and prone. smallbore rifles have are all from across the pond but you will still find some remington 37s and winchester 52s still on the line at prone matches.