DINK: I have from time to time relayed here how my close friends here in SW Montana have a "family" 223 Remington Rifle they use to fill their freezers with every year.
This family consists of 4 daughters a mom and a dad all who Hunt.
They harvest around 6 to 10 animals a year with their Remington 700 in 223!
I have seen members of this family take at least 10 animals first hand - all were one shot kills and IIRC all were DRT!
This list of witnessed animals includes Mule Deer, Antelope and Whitetailed Deer.
A few years back I saw one daughter kill a 31" Mule Deer Buck with one shot from the 223!!!
This was a BIG bodied Deer by the way!
The same daughter killed a Mt. Goat a few years earlier (again with one shot!) using the families trusty 223.
The family uses Remington factory ammo (55 grain PSP's by Remington) for their Hunting needs.
Never heard of a "blood trail lost" from my friends.
I think the "plan" with the 223 Remington and medium size game is to shoot them in the heart/lung area and let the bullet "explode" therein - this results in a quick and humane kill.
If this is accomplished (the correct shot placement and a good bullet like the 55 grain Remington PSP!) you will not need to be looking for a blood trail.
I have used 22 centerfires on Deer and Antelope a few times myself - I would certainly NOT use a 100% copper bullet (like the TTSX's!) on them.
Try the 55 grain Remington PSP's next year.
Please extend my congratulations to your young Hunter.
Hold into the wind
VarmintGuy