Best .223 bullet for deer?

[petey]

I suppose "opinions" are welcomed as long as they are somewhat informative So why am I asking the question?

Well I'm building a custom fitted .223 for my 6 yr old to hunt deer with this year under our PA Youth Mentoring program. He's a heck of a shot with his Crickett, has already hunted spring gobbler with me. He'll be hunting squirrels in a few weeks when that opens up. B/c he's so small, I'm starting him out small. Obviously he's a good shot already otherwise I wouldn't be considering this...but I feel he's ready to take on some bigger game and I'm building a gun with very low recoil that we can plink with every day until November and getting him to the point where he can drive tacks every time at 100 yards.

Laugh now, but with me by his side, there isn't a pop can safe at 50 yards when he shoots his Crickett, handeling the gun by himself.

Ethical? You think he's too young, too small...I don't care about those comments. I'm building him the gun, he's probably already a better shot and twice as safe as than half the guys I work with (after listening to some of their hunting stories and missfires, etc..). I want a bullet that will get the job done for him when it's time to make it happen.