A Mercedes CLK was stolen from Hedingham Drive, Dagenham, in August 2018 and was found in Daniell Drive, Colchester, in October after being reported abandoned.
The car, which had false number plates, was searched and inside were a .22 rifle and three sawn off shotguns. There was also ammunition for two of the weapons.
Fingerprints belonging to Oliver Simons and Lewis Marsh were found on the wrappings of one sawn off shotgun and their DNA was found on two other weapons.
Following an investigation, the pair were charged with firearms offences in June 2019.
Marsh pleaded guilty to three counts of possession of a prohibited weapon, one count of possessing a self-loading rifle and one of handling stolen goods when he appeared at Chelmsford Crown Court in October this year.
Marsh, 24, previously of Hawkins Road, Colchester, and Simons, 27, of Hickory Avenue, Colchester, were both jailed for a total of eight-and-a-half years each.
The weapons, ammunition and encrypted smartphones will be destroyed.
Detective Inspector Steve Nelson said: “These guns could have caused immense harm in the wrong hands and will now be destroyed.
“Fortunately few people will ever be affected by gun crime and we are working tirelessly to keep it that way, by targeting organised crime and individuals involved in such violence.”