Dummer, who was in another hunting party, was only 16.3 metres away when he got Mr McDonald in his scope and fired once, shooting him in the head.
The public gallery at the court was packed with family members and supporters of both men.
Dummer's family reacted with tears at the jail sentence.
But outside court Mr McDonald's parents spoke of their relief at the prison sentence.
Cyndy McDonald said no sentence would have been long enough.
"It's a message to other hunters in the bush that they know that this is what can happen - a term of imprisonment."
She said the jail term would hopefully help impress on young hunters the importance of identifying their targets.
"That's the rules and unless there's a harsh penalty, it's not going to stop."
Ranald McDonald said they didn't want any other family going through the pain they had been through.
He said the last six months had been "hell".
Mrs McDonald said they had years of grieving ahead of them but today they were going to starting the process of healing.
Detective Senior Sergeant Sean Hanson from the Wairarapa CIB said the sentence sent a message to hunters to identify their targets "beyond all doubt".
"I urge all hunters to ensure that they acknowledge this principal before they pull the trigger. It's that simple."
He said if hunters did that, accidental shootings would stop.
"The real tragedy is, these sorts of incidents are preventable.
Before imposing his sentence, Judge Hobbs said he believed Dummer had accepted responsibility for the Mr McDonald's death.
He said in the last six months three people had been killed in hunting accidents and he had to hand down a sentence that would send a message to other hunters.
Defence lawyer Andrew Davie said Dummer's "catastrophic" mistake would live with him forever.
Emotional victim impact statements by Mr McDonald's family were read to the court.
Mr McDonald told the court that when he was told his son was dead, his life changed forever.
"I have never cried so much ... telling people that Cam had been shot and killed was so difficult."
Mrs McDonald told Dummer he had broken her heart and ruined her life.
She said she struggled every day to be the wife, mother, sister and friend she used to be before the shooting.
"I have been given a life sentence of heartache and insecurity."
His brother, Jonathan, said Mr McDonald was his "guardian".
"Now there is not an hour of the day that passes that I do not think of Cam and the laughs we've had."
His uncle, Cameron McDonald, said there was "great anger" in the family at how his death could have been avoided if Dummer had stopped to identify his target, he said.
Mr Davie this afternoon made an urgent application for bail while an appeal against the sentence is lodged with the High Court.
But Judge Hobbs declined the application and sent Drummer back to prison.
Mr Davie said when the appeal reaches the High Court he would argue that Judge Hobbs did not exercise his discretion when handing down the nine-month prison sentence because the three previous cases he drew on all resulted in home detention sentences.
Bail should be granted in the interim, Mr Davie argued, because Drummer would lose his job if he went to prison, but could keep it if he was on home detention.
However, Crown prosecutor Dale La Hood said it was only two weeks until the appeal would be heard, and some people took longer breaks than that from their jobs.
Judge Hobbs agreed with Mr La Hood, but also said he could see that there was grounds for an appeal.
