Oliver Kierans, of Bailieborough in County Cavan, was also sentenced to eight years for possession of a sawn-off shotgun and 12 years for possession with intent to endanger life.
He had pleaded not guilty to murdering his wife Patricia Keane in 2013.
He was found guilty of her manslaughter in February.
During his trial Kierans had said he had intended to take his own life on 5 September 2013 when he and his wife visited the family home.
They had been separated for a number of months.
He said that he picked up the shotgun and it went off, hitting his wife, the mother of his four children, in the chest and causing severe injuries leading to her death.
Kierans then went to a bar in Bailieborough where he pointed the gun at a member of the police before his arrest.
The judge said that when passing sentence she took into account that Kierans' four children had stood by him and that he was a loving grandfather.
The sentences will run concurrently.
A man has been sentenced to nine years in prison for the manslaughter of his wife of 33 years in the Republic of Ireland.