Fearon, 30, was hit in both legs when Norfolk farmer Tony Martin fired at him and Barras, 16, at his farm near King's Lynn. Martin is serving life for Barras's murder.
Mr Justice Penry-Davey told the appeal court in London that a psychiatric report concluded that Fearon suffered symptoms of post traumatic stess disorder after his friend's killing and that the incident may have been "a life-changing experience".
Fearon's counsel had claimed an unfair disparity between his sentence and the two-and-a-half year term of his co-accused, Darren Bark, who "had a worse record".
But the judge, sitting with Lord Justice Mantell and Judge Fabyan Evans, said Fearon's sentence, imposed at Norwich crown court on January 10 for conspiring to burgle Martin's home, could not be faulted.
Fearon, of Newark, Notts, was refused leave to appeal against length of sentence.
