Jimmy Stevens, 19, and Mark Thorne, 36, were convicted last week after a three-week trial at Guildford Crown Court.
Relatives of the pair shouted in disbelief as the jury returned a unanimous guilty verdict to a count of robbery in little more than an hour and a half.
As Stevens was convicted of a further charge of possessing a firearm with intent, relatives — who had to be restrained by police — shouted “liars” at detectives involved in the case.
Stevens and Thorne, who both denied any part in the robbery, were told by Judge John Bull to brace themselves for a prison sentence.
The jury had been told how Stevens and Thorne stole £1,500 from a Pirbright post office during an armed raid in December 2001.
Witnesses described how one of the men, said to have been Thorne, of Longacre, Ash, “manically” waited outside the post office by a Ford Orion.
Meanwhile inside the building, a balaclava-clad Stevens, of Winchester Road, Ash, used a hand gun to demand cash before they drove off.
A motorist who followed the Orion told the court that when he caught up with the robbers they had set the car on fire and driven off in a second getaway car — a VW Golf — which Thorne claimed to have sold the day before the robbery.
The Golf was later found burnt out and a melted handgun was discovered in the boot.
At the time of the robbery, Thorne said he was at work in Aldershot, which was confirm-ed by co-workers.
But the jury was told by Judge Bull that they had to determine whether his alibi was a “convenient shield” as he failed to give the same explan-ation to officers when first arrested in January 2002.
Stevens claimed he was Christmas shopping in Aldershot, and challenged detectives to “check the CCTV tapes” of the town centre to prove it.
All witnesses to the robbery failed to identify either man through identification parades, with one claiming that one of the robbers was 6ft 6in tall. Neither Stevens or Thorne is more than 6ft.
But the jury was told that DNA evidence linked them to the robbery.
Items, including two sleeves from a fleece-type top, said to have been used as balaclavas, and a sock, were said to have been discarded from the getaway cars.
Forensic expert Michelle Hanslip said that, in her opinion, a DNA profile found on one of the sleeves had a one in a billion chance of not being from Stevens.
But a complex analysis of two DNA profiles found on the other balaclava proved less conclusive.
Dr Lesley Sawyer, a colleague of Ms Hanslip, said the profiles were 50 times more likely to have come from Thorne and another person rather than two unknowns.
Grilled by the defence, both experts said they could not establish whether the sleeves had been worn as balaclavas when the DNA was deposited or as a normal garment prior to the sleeves being cut off.
Thorne and Stevens will appear at Guildford Crown Court on Wednesday February 26 for sentencing.