Welcome to the world of hunting! With your zero experience, you will enjoy all of the adventures that await so get out there and explore. My first recommendation is to seek out a friend with hunting experience to help you with the basics. Focus on safe, fun, and ethical. Specific to your question; I would avoid the 5.56 for small game but for different reasons than mentioned thus far. My rationale is safety. Squirrels in trees, rabbits at close range on the ground, etc... all represent safety risk with a 5.56 and a .22 is much more suitable and adequately lethal. Even with a .22lr, the type of bullet design and velocity will matter regarding lethality. I would recommend using Hollowpoint ammo above 1070fps until you get more time under your belt. Have fun hunting and as you gain experience - help introduce a new person to hunting.