The 15-year-old appeared at Bradford Crown Court with 20-year-old accomplice Waqas Hussain, who was jailed for 12 years in his absence after he absconded during the trial.
A jury had convicted Hussain, of Fearnsides Terrace, Girlington, of five counts of robbery as well as possession of a firearm.
Among the offences Hussain was sentenced for was a robbery in St Matthew’s Grove in Wilsden last October, where a man in his forties was dragged from his Volkswagen Golf R and tasered by men with weapons.
He was also convicted of a robbery in Halifax Road in November, where a lone female with a baby was threatened with a firearm before a VW Polo was taken. The vehicle was later recovered.
Hussain was also found guilty of an offence in The Grove, Idle last November, where he and his teenage accomplice robbed a man in his forties, who was struck with a pick axe and dragged from his Volkswagen Golf GTD.
The teenager was convicted of two robberies and he also found guilty of three attempt robberies, dangerous driving and a make off without payment offence.
He was sentenced to six-and-a-half-years in a young offender institution.
Hussain, of was not present in court for the sentencing after absconding during the trial. Enquiries are continuing today to locate him.
Speaking after the sentencing, Detective Inspector Ian Bryar, of Bradford District CID, said: “These were very serious offences in which Hussain and others used violence to steal desirable cars from vulnerable victims.
“Our enquiries into these incidents and other similar matters are continuing to identify the others who took part in these terrifying robberies.
“Violent crime will not be tolerated and the sentences passed should serve as a deterrent to others.”
Anyone with information about those suspected of being involved in violent crime can contact police on 101, or pass information anonymously to the independent charity Crimestoppers on 0800 555111.