An ice addict who murdered a war veteran on the eve of his 90th birthday during a burglary in Victoria's west has been jailed for 16 years — receiving a considerable discount on his sentence.

Jonathon Cooper, 29, and his friend, 40-year-old Adam Williamson, broke into Ken Handford's home in Springbank, near Ballarat, in September 2015.

The pair tied up the decorated World War II veteran by his wrists and legs before Cooper stabbed him 13 times in the back after "losing control", the Victorian Supreme Court heard.

They stole cash and war medals before leaving Mr Handford to slowly die, tied up in his bedroom.

His body was found the following day on his birthday.

In sentencing Cooper, Justice Jane Dixon told the court he and Williamson had initially planned to rob Mr Handford's home, believing he had up to $30,000 in cash stashed at the premises.

"You deliberately targeted an elderly and vulnerable victim," she said.

"Your angry and violent impulses took hold and brought out the worst in you."

The court heard Cooper was sexually abused as a child and wrongly believed Mr Handford was a paedophile.

Justice Dixon said Cooper had made full admissions to prosecutors and agreed to give evidence against his co-offender Williamson if required.

She told the court that if he had not offered that assistance she would have sentenced him to 27 years in prison with a non-parole period of 25 years.

Instead, he will serve a minimum 13 years in jail.

Following the burglary, Cooper and Williamson split the almost-$4,000 in cash and other valuables they had stolen, the court was told.

Mr Handford's family cried during the sentencing.

Justice Dixon told the court the family was shattered by Mr Handford's death.

In a separate hearing, the Victorian Supreme Court allowed Williamson to change his plea to not guilty over his alleged role in the murder.

He will face trial later this year.