John Lowe, who killed Christine Lee and Lucy Lee in February, was given a minimum sentence of 25 years.
The jury at his Guildford Crown Court trial was told Lowe wanted the women "put down".
Surrey Police has apologised for returning Lowe's confiscated guns to him seven months before the shooting.
Sentencing Lowe, Mr Justice Singh praised the "extraordinary courage" of Lucy Lee after she returned to face her killer after making a frantic 999 call.
He said that, having heard the evidence, he had come to the "clear conclusion" the 82-year-old had intended to kill both of the women.
"You shot Lucy Lee in the back of her head after she made the 999 call, then reloaded your gun and pursued her outside the cottage, with the intention of making sure that this time she died," he said.
In a victim impact statement Stacy Banner, Lucy Lee's sister, said she was "haunted by what Lowe has done".
She said Lucy was the "big sister who comforted and preceded me" and the murders had left her struggling to eat and sleep.
Outside court, she said: "I'm relieved it's over. He's never getting out."
Ms Banner has criticised police for returning guns to Lowe just months before he carried out the shootings.
Surrey Police has admitted the decision "was flawed and did not meet national standards".
Three Surrey Police employees are being investigated for gross misconduct by the Independent Police Complaints Commission (IPCC) over the decision to return the weapons.
Christine Lee's sister, Julia James, said she felt "despair, physically and emotionally" since the death of her two relatives.
"I miss them more than I can say," she said.
At the start of the hearing, prosecutor Mark Dennis QC said Lowe's advanced age should not "dramatically" reduce his sentence and the "starting point" for a double murder of this kind would be a minimum of 30 years in jail.
Surrey's Police and Crime Commissioner Kevin Hurley said as the trial was now over the inquiry could focus on why Lowe was given back his guns.
Factors which would be investigated included whether the decision had been made because of "human error by negligence, as a genuine mistake, or as a result of funding cuts to backroom staff", he said.
An 82-year-old man has been jailed for life for murdering his partner and her daughter who he shot at close range at his puppy farm in Surrey.