.243 not a good rifle for a youth? Not sure I understand that one, but certainly you are entitled to your opinion. I can only tell you from my experience...my son has shot 13 with his, all are dead...most died within 30-50yds. A couple fell on the spot. He did have a couple that went about 75yds, running dead.

Deer running off too far is usually indicative of either poor shot placement, or poor bullet performance. Not the caliber. I've seen guys with .300 mags have deer run more than 100yds...it wasn't the caliber.