It's not really surprising that the actors on The Walking Dead don't do most of their own stunts. What is sort of surprising is that Carl Grimes's stunt double on The Walking Dead is a 29 year old woman named Emily Brobst.
Here's what is supposedly a picture of Emily and Chandler Riggs, the actor that plays Carl, together. Can you tell who is who?
This is really common. In Stand By Me, my stunt double was a woman, because I was skinny and lanky and all the male doubles were too stocky to double me. I'm sure that it's a similar situation with Chandler.