Mark Anthony Munro, 53 of Campbell, was sentenced to 18 years behind bars in May this year, two months after a jury found him guilty of helping another man, Sam John Melkie, 53, rob the van in broad daylight in May 2004.

The pair were recruited to carry out the heist after an inside man and a mastermind gathered intelligence and planned the robbery.

They waited in a bus shelter near the Mawson Club for the Chubb van to arrive.

Melkie then walked up to the guards with a pistol and demanded they hand over the money.

The pair took $151,000 in cash bags.

Then, in an act described as ''completely unnecessary'', Munro shot a guard in the face with a shotgun.

The guard survived but was left with more than a dozen shotgun pellets in his body.

Munro was caught after cigarette butts matching his and Melkie's DNA profiles were found at the bus stop.

But Munro has now appealed against his conviction and his sentence.

Barrister Shane Gill told the ACT Court of Appeal on Monday that there were issues with the circumstantial case against Munro, and the trial judge's directions to the jury.

Mr Gill said the sentence was ''simply too much'', and failed to properly take concurrency into account for the two charges Munro faced; aggravated robbery and recklessly or intentionally inflicting grievous bodily harm.

Mr Gill also criticised the trial judge's finding Munro was subject to conditional liberty at the time of the armed robbery, without giving his client a chance to reply.

The ACT Court of Appeal has reserved its decision.