Peter Roberts, 46, shot Daphne Masterson in the head then stopped her getting help for about 36 hours.
Truro Crown Court heard the pellet was lodged in Ms Masterson's skull, resulting in a serious brain injury.
Roberts, from Millendreath, near Looe in Cornwall, was jailed for one count of wounding, two counts of possessing firearms and one of affray.
The court heard Roberts shot his lover in the early hours of 28 September 2014, but Ms Masterson did not call 999 until the morning of 29 September.
Paramedics arrived at her home in Millendreath and found her with a wound to her right temple and a bloody towel on her shoulder.
Judge Simon Carr said: "It must have been obvious she required medical attention, but you seemed to have attempted to cover it up."
Roberts threw a rifle off nearby cliffs on the morning of 28 September, the court was told.
He was banned from holding firearms due to previous convictions for violence, but police discovered he had bought a .177 air rifle in Liskeard and a .22 air rifle from a neighbour.
Medical experts found the main part of the pellet had gone Ms Masterson's brain.
Her daughter said in a victim impact statement that her mother struggled with everyday tasks and regularly burst into tears as a result of the shooting.
Ramsay Quaife, in mitigation, said Roberts was "a hardworking, decent man".
He was sentenced to 30 months for wounding, 15 months consecutive for two counts of possession of firearms and a further 15 months for a separate charge of affray.
A man who shot his lover in the head with an air rifle has been jailed for five years.