But Hamish escaped major blood loss because the heat of the bullet partially cauterised the wound. The burned flesh later had to be removed when stitches were required.
James said his son at first didn't realise he'd been shot.
"He didn't understand, but I did. So I was in immediate shock, but I had to keep myself alert, to ascertain the damage that had been done.
"His eyes were wide open, and he says 'what has just happened'.
"He didn't feel anything, because he was so close to the bullet it cauterised his skin."
James described it as a "nightmare situation", that could have pulled their close family apart.
"He'd just had a son; 5-months-old," he said.
"He was down on the first day of his annual holiday, with his wife, down from Auckland."
James struggled to cope with what had nearly happened.
He bought cards to apologise to all of his loved ones, including Hamish, Hamish's wife, his own wife, Hamish's in-laws, and two of his close friends.
"I wrote to them to apologise for the accident and the harm, the grief I'd caused.
"Going through the hospital was pretty traumatic. Telling my father and mother was traumatic. Telling my son's in-laws was traumatic.
"But they've all accepted my apologies, and that it was a mistake."
James agreed to talk to the Herald in the hope that being open about his experience could stop others from going through the same thing.
"There are seven basic rules, for firearms. Fail to do one, and it could be catastrophic.
"I failed to do one.
"Every time you've got a gun, keep it empty until you've got a target in front of you."
Police prosecutors said James Blair had contradicted basic firearms safety, including to treat every firearm as loaded, point them in a safe direction and load only when ready to fire.
Firearms expert and former president of the Deerstalkers Association Trevor Dyke said having the gun loaded with the safety off was a "major no-no".
"What he could have done was have a semi-ready state, where the bolt is partially open and the round is partially exposed.
"Then the gun couldn't go off if anything happened.
"You shouldn't be taking a snap shot. You should be walking along in a state of semi-readiness, then close the bolt when you see your target."
James appeared in the Hutt Valley District Court on Wednesday, after pleading guilty to careless use of a firearm causing injury.
He was supported in court by his wife, father, and his other son.
Hamish wrote a letter to the court to explain he couldn't attend from Auckland but that he supported his father.
In court, Judge Arthur Tompkins noted that "reading the emotional impact review, the son says the father has suffered more than he has as the victim".
James Blair was ordered to donate $3000 to the Mountain Safety Council, or a comparable organisation.
It was his first appearance before the court.
He was discharged without conviction.
