I don't usually get involved with these types of discussions but here's my two cents. I chose a .223 for a youth rifle when my kids started hunting, paired specifically with a 60gr nosler partition, recommended via the terminal ballistics guy from down under.
We have put down quite a few deer, one first timer just this morning, probably more than 12 in total. All one shot bang flops except today. It ran 30-40 yards and was shot a second time broadside, game over. During gutting I found the buck was likely seconds from lying down to die, his liver and one lung were gone.
I chose it because kids can become confident with the hunting rifle on gophers and targets. They all go into hunting season with a pile of dead gophers and hundreds of shots with the same gun under their belt, no sign of nervousness or apprehension whatsoever. By deer season that gun is an old friend.
A side benefit when you have as many kids as I do is that meat loss is minimal, the most I've had to leave is maybe the size of a tennis ball.
We keep the shots close and they never hesitate. I talk them through shot placement over their shoulders and the rest is muscle memory.
This discussion needs a strong warning though. Bullet choice and shot placement are critical. Period. The Partition is excellent, transferring all it's energy in the deer, penetration is out the other side or under the off side skin, 80-90% weight left. When my Partitions run out I'll be using a 50 or 53 grain Barnes assuming the Nosler bullet still won't be in stock. Copper solids need to be light for caliber and driven as fast as you can. Not heavy for caliber and slow, they won't open.
Those choices would work well in all the slower twist rifles out there at reasonable ranges fired by a good hunter determined to make a clean shot.
