In my opinion, the 7x57 is the nicest rifle for plains game (as long as you put in the extra yards on your stalk). I have dropped, blues, hartebeest, kudu, zebra, impala, blesbok, mtn reedbuck, duiker and feral dogs with my trusty old musgrave built 7x57. Never experienced any sort of bullet failiure from factory ammo or reloads. Let us not forget Mr Bell and his 7x57...
In reading a couple of other threads about "what to get my kids for their first rifle" I rate the 7x57 as the choice.