Liam Turner and Simie McGinley targeted a newsagents in Wakefield and a camp site in north Yorkshire over two days in August last year.
Turner was also responsible for two “evil” violent attacks on men in Wakefield city centre. One involved him following a disabled man into a pub toilet and breaking his jaw.
Leeds Crown Court heard a masked man went into Sunnyhill Stores, Wrenthorpe, at 8.55pm on August 27 and pointed the weapon at the woman working behind the counter.
She was ordered to hand over cash and cigarettes worth £400.
The court heard the victim has suffered nightmares and anxiety since the incident.
The robber got into a Ford Puma driven by a second man. Witnesses took the number plate of the vehicle and it was traced to McGinley.
The next day the pair carried out a robbery at the camp site near to Bolton Abbey.
The owners, an 84-year-old man and his grandson were in the lounge of their home, which doubles as the reception area for the site.
Turner and McGinley walked in with their faces covered and threatened them with the gun and ordered them to hand over cash.
The victims were told that there was no cash on the premises. They were then ordered to hand over the Rolex watches from their wrists, worth around £9,000 each.
During the robbery one of the men threatened to hit the 84-year-old man.
Police found the Ford Puma burnt out close to the site. They then obtained camera camera footage of the vehicle being driven to the area in convoy with a Renault Clio.
The Clio was also traced to McGinley. The vehicle was recovered by officers who found a letter inside which was addressed to him and a pair of socks containing his DNA.
Turner was released on bail and attacked a vulnerable disabled man in the toilets of the Wakefield Tavern on October 2.
Turner punched and kicked him in face before taking money from him which he had won on a gaming machine.
A member of staff found him on the floor covered in blood. Turner carried on drinking in the pub and when he was challenged about the assault he smirked and said: “He’s fallen.”
The victim had to undergo surgery for a broken jaw. In a victim statement he described how he now felt a “shadow of his former self” as a result of his ordeal.
He said: “I look like something from Frankenstein.”
“I am an honest man who would not do wrong and look what has happened to me.”
Turner was also among a gang who attacked a car containing a group of men who had been enjoying a night out in Wakefield city centre on October 22.
The gang then followed the car in their own vehicle and forced it to crash. Turner then got out and attacked one of the men as he tried to run away.
Turner punched and kicked him several times to the face, leaving the victim with a broken jaw and fractured eye socket.
McGinley, of Ashbrook Close, Ossett, was jailed for ten years after pleading guilty to three offences of robbery and three of possession of an imitation firearm.
Turner, of Park Avenue, Lofthouse, pleaded guilty to three offences of robbery, three of possession of an imitation firearm, two of causing grievous bodily harm, common assault and criminal damage. He was sentenced to 14 years.
Judge James Spencer, QC, said: “You were released on bail and you committed some evil offences.
After the case, Detective Inspector Tim Hunt of Wakefield District CID, said: “We are very pleased with the sentences both men have received for what were serious offences committed with a firearm.
“On both occasions their victims were left terrified after being threatened with a shotgun by the men, who were also wearing masks.
“Both of these prolific offenders were arrested following close collaborative work by Wakefield detectives and our partners in North Yorkshire.
“These robberies were highly unusual offences for the areas they took place in and I hope the strong sentences given to these men will be of some comfort and reassurance for residents.”