David Dargan, 32, John Groom, 35, and Patrick McDonagh and Richard Smith, both 37, were members of a gang which burst into the McColl’s store in Atherton last August.
Police say staff at the Car Bank Street shop were threatened, with one victim repeatedly punched in the face during the terrifying incident.
The robbers, who were caught on CCTV, fled the scene with just a small amount of cash and stamps, and ran towards a Vauxhall Vectra, which had been parked nearby.
Detectives later confirmed that, after a series of car changes, the gang was tracked down to an area around junction four of the M61, where the elderly male driver of a Toyota Yaris was attacked on the slip road, in an attempted carjacking.
The incident also saw a woman dragged out of the car before police, after a short chase, eventually managed to apprehend all those responsible for the earlier McColl’s raid.
Dargan, a Salford man of no fixed address, Groom, of Manchester Road, Worsley, McDonagh, of Ridge Crescent, Whitefield, and Smith, of Pegwell Drive, Lower Broughton, were both later charged with the Atherton robbery, for which they have all now pleaded guilty.
Another attempted robbery charge, relating to the aborted carjacking, was also admitted by Dargan, Groom and Smith.
Smith and McDonagh have also confessed to being part of a wider robbery conspiracy which saw a series of cash raids on security vans across Greater Manchester.
One attack on Halifax Bank in Sale, in February, saw £195,000 stolen from guards, with tens of thousands also stolen in similar incidents at Barclays in Oldham and Hyde and the Royal Bank of Scotland in Stockport.
All four have been remanded in custody by a Manchester Crown Court judge to face sentencing for all matters on April 13.