I started my son out with a 257 Roberts. When he got a bit bigger, we chambered it to 257 Ackley. He has made clean kills on several pronghorn, deer, and an elk with no problems.

He is loading 120 gr Nosler Partitions at 2900 fps, and they slam in there real well with excellent penetration.

I might try it on small and medium plains game this year.
It is nice and light, and a pussycat to shoot.