re: First deer down for my nine year old. Need help

Sorry to hear about the lost buck, but glad to hear about the doe kill. Not trying to start a caliber war, but from the perspective of a fellow father, I've got some suggestions.

When my son started hunting at the same age, I put restrictions on what he was allowed to shoot, in both distance (100 yards and closer) and presentation (standing still and basically broadside or slight angling shots). The straight frontal is a difficult shot, even in the hands of a skilled hunter. The best presentation w/ the straight frontal shot is when the deer's head is down (feeding). That gives an excellent angle to the spine and a chest shot that should exit. What probably happened w/ his buck is one of two things:
1. The bullet hit low in the brisket.
2. The shot was straight on/nearly straight on, only clipped a lung, didn't exit (lodged in stomach, intestines or ham) and left little blood trail.
Your description sounds most like #1. If it was #1, the deer probably won't be found. If it was #2, the deer may be found, but will be some distance away.

I'd suggest putting some limitations on the shots he's allowed to take. I'd also consider something like the 260 Rem, 6.5 CM, 7-08, 308, 270 or 30-06, with managed recoil loads whenever possible. It's true the 243 has killed (and will continue to kill) a bunch of deer. Nevertheless, I personally think there are better deer hunting rounds, especially for the non-expert hunter or when the presentation is marginal. One doesn't have to shoot a 300 Mag to have a round that's more powerful than the 243, yet manageable. For example, a reduced recoil 308 Win load has less recoil than a full power 243. At limited distances, trajectory's not going to be a problem w/ the managed recoil load.

Congrats on being an involved dad. It's good your teaching your son to enjoy God's wonderful creation. This is just the start of MANY fond memories.