I think the 243. would be fine. My son is 8 and about 50 pounds. He shoots one off the bench and, handles it well. He is just too small tohold it for offhand. Take him with you to the shops and let him handle a few.I personally started out with a Marlin 336 in 35 Rem. But my father was sadistic and got a kick out of it. He may be surprisingly recoil tolerant. Think about the Marlin 1894s'. Weatherby sells a Vangaurd youth model that comes with a full size stock. You can get it in .243 and, that would keep you from buying another rifle later.