Dave is not a mean yet because he is not ready to take responsibilities for his actions. Dave is mad because people don't think or treat him as a man. Dave's definition of manhood is making people scared. That is why he wants a gun, to scare people. That is not a sign of adulthood.
My definition of manhood is being able to take responsibilities for your actions and doing the right thing for yourself and others.
Do I agree with Dave's definition of manhood/adulthood, no because his definition of manhood makes no sense. Scaring people does not make you a man. So he wants a gun to scare people and when he does get a gun people end up laughing at him. He kills Jenny, the mule, and he lies about how she dies. But first he tells his mom that he will bring the gun home to his mom but he does not.
He keeps it. He shoots Jenny and does not take the responsibility for killing her either. "It wasn't me"(p.14) Them when he gets caught he lies to Mr. Hawkins and his family about killing Jenny. Dave, after he gets caught and finds out that he has to work off his debt for killing Jenny, runs away but when he is leaving he looks at Mr. Hawkins house and dreams of shooting at it and then he leaves on a train to an unknown destination. "I know, I'll runaway"(p.19)