An experienced shooter who smoked 35 bongs and drank 42 stubbies before shooting dead an intruder at his workshop in Melbourne's north has been sentenced to eight years in prison.

Ivan D'Angelo, 39, pleaded guilty in the Victorian Supreme Court in August to the manslaughter of 27-year-old Wade Vandenberg after a jury found him not guilty of murder.

The court heard D'Angelo was disturbed by three men trying to break into his Thomastown business one night in March last year and panicked.

D'Angelo was living in the warehouse at the time and prosecutors told the court he "lined up the victim's head" and shot him in the middle of the forehead from the window of his bedroom.

But Justice Lex Lasry rejected that argument, instead finding the gun went off by accident after D’Angelo panicked and pointed it out the window and he hadn’t meant to shoot anyone.

The court heard Vandenberg and two associates tried to enter the property to steal an engine part for Mr Vandenberg's car.

In sentencing Justice Lasry told D'Angelo it was a tragedy he had not reached for his phone instead of a loaded gun.

"The fact that his death was so avoidable in so many ways makes it all the more tragic," said Justice Lasry.

"No reasonable person should ever point a gun at another person and pull the trigger."

The court heard D'Angelo had consumed up to 42 stubbies of beer and as many as 35 bongs of marijuana in the hours leading up to the shooting.

D'Angelo earlier told the court he did not realise his gun had a live round in the chamber when he shot Vandenberg.

Justice Lasry said he did not accept the prosecution's argument that D'Angelo's offending was "in the higher range of seriousness" for manslaughter.

"The crime came to you rather than you going out to commit a crime," Justice Lasry said.

"Your chances of reoffending are very low ... you're well aware of your stupidity.

"I'm convinced you did the best you could to tell the truth about what happened."

He will serve a minimum term of four and a half years.

Editor's note: The reporter incorrectly reported as fact that Ivan D’Angelo lined up Wade Vandenberg with his gun and pulled the trigger. This was the prosecution’s argument, but Justice Lasry rejected it. He found in favour of D’Angelo’s defence – that the gun discharged by accident and the bullet struck Mr Vandenberg.