I have a youth Weatherby Vanguard in .223 that I start my sons out deer hunting with. My oldest son killed two deer with it (one fawn, one small 8-pointer). My middle son killed a nice doe this year.
We use Hornady Superformance 55 grain GMX ammunition and restrict our shots to < 100 yards. I have been pleased with the results so far. The boys have taken three shots, killed three deer, and none went very far.
I think it's acceptable, but I do like to move up to a larger round when they're ready. My oldest moved up to a .308 shooting reduced recoil ammo last year and is now shooting a 6.5 Creedmoor. I will probably do something similar with the middle son.
So my personal summary is that the .223 works but is non-optimal. I do appreciate that with modern bullets it gives youth a chance to make humane kills without too much recoil. Always a bonus.
