A 223 would be fine for a deer rifle but you need to make sure the (youth) person can hit the kill zone. I would suggest the 243.
A rifle with a 5.56x45 chamber can utilise .223 Remington cartridges. A rifle with a dedicated .223 Remington chamber cannot accommodate 5.56x45 cartridges. A rifle with a .223 Wylde chamber can accommodate .223 Wylde, .223 Remington, and 5.56x45, but neither a rifle with a 5.56x45 or a .223 Remington chamber can accommodate the .223 Wylde cartridge.
Kel Tec SU16
.223 Remington can be cycled in a 5.56x45 rifle; 5.56x45 should not be cycled in a .223 Remington firearm.
no
NO the .223 is a totaly diffrent round than the .223 WSSM
The 223 is considered a Short Action rifle.
you can fire both 5.56 and .223 ammo in a rifle chambered in 5.56...but not the other way around! In a rifle marked .223, you should fire .223 ammo only
It depends on the condition of the rifle.
No.
.223 Remington ammunition can be fired safely in a 5.56x45 rifle; 5.56x45 ammunition cannot be safely fired in a .223 rifle. In the case of some partially imported rifles, they are marked .223 Remington in spite of having 5.56 chambers. This is done for compliance with BATFE laws regarding importation of certain firearms types. If in doubt about the compatibility, call the manufacturer - they're the ones who would know best.
.223 is considered a short action cartridge.