Happy looking kid, great looking gun, and beautiful coyote! Congrats.
I use to think the same about the .223 until I let my kid use his for a deer. My oldest has now shot several deer with his AR - .223. None of them have ran as far as when shot with my .308, but he shoots open sites and never takes a shot farther than 20yds. My .308 slides right through them, his .223 seems to release a lot of energy into them and does a LOT of damage. Even though his .223 has been highly successful at killing deer, I still wouldn't want him shooting a deer at more than 100yds with it.