Jonathan Williams, 30, of Mixenden Court, Mixenden, Halifax, raided Ladbrokes at Keighley Road, Ovenden, along with a 17-year-old acc-omplice who pointed a replica gun in "gangster style" at terrified workers and customers.
The youth, who cannot be named for legal reasons, has already pleaded guilty to the robbery and was to be sentenced today.
Gavin Howie, prosecuting, told Bradford Crown Court the pair ordered seven customers who were in the betting shop on to the floor, and demanded cash from terrified workers, including an eight-and-a-half month pregnant cashier.
The mum-to-be is thought to have been on her final shift before beginning maternity leave.
Mr Howie, said: "Williams shouted at them to give him the money and he was passed two trays worth £530.
"One of the customers in the shop, Mark Brennan, refused to get down on the floor because he said he recognised the gun as a fake.
"He picked up a stool and chased the men out of the building." The two robbers got away in a maroon Vauxhall Carlton but were arrested a few days later.
DS Chris Wood, of Calderdale police, speaking outside court, said: "This was a crude and brazen robbery with a very dangerous weapon used around a lot of people.
"It is the right sentence and it reflects the seriousness of the offence."
Another accomplice, Nathan Hutchinson, 18, of Hawthorn Way, Hali-fax, pleaded guilty to attempting to pervert the course of justice, after he hid the gun used in the raid at his house.
Gerald Hendron, for Hutchinson, told the court he was persuaded to hide the weapon and did not know what it had been used for.
He was sentenced to 200 hours unpaid work with a two-year supervision requirement.
Hutchinson's family cheered from the public gallery as he walked free.
Judge Jonathan Dur-ham Hall described the raid as "a very serious armed robbery" and said Williams was the instigator.
Williams pleaded guilty to the robbery, which happened at 9pm on July 18, and was jailed for seven and a half years.
He also was sentenced to a further 18 months after pleading guilty to another theft of £16,000 of Velux windows from a former employer.