Two men who robbed a southside liquor store with a replica pistol will spend their weekends in jail for the next two years.

Justin Hart pleaded guilty in the ACT Supreme Court to aggravated robbery and was ordered to serve 2½ years' periodic detention.

Co-offender Joseph Wayne Kelleher, who also pleaded guilty, was convicted of aiding and abetting aggravated robbery and was given two years' periodic detention.

The court heard a masked Hart entered the store at Chisholm Shops about 8pm in August 2010. He pointed a pistol at the attendant's face and demanded money and ''smokes''.

The staff member handed over more than $1500 in cash and 25 packets of cigarettes.

Kelleher acted as getaway driver. Passers-by followed the car, noting its number plate.

The pair were later arrested and a mask was found in the back seat of Kelleher's ute.

Kelleher recorded a blood-alcohol reading of .086.

A later search of Hart's business premises in Hume located a replica handgun matching the description given by the store attendant.

In sentencing, Justice Richard Refshauge noted the pair had a history of drug and alcohol abuse but had since reformed their ways.

The court heard Kelleher estimated he had drunk 36 standard drinks and injected two grams of speed on the day of the incident.

Hart had been on a bender for about four days.

Neither man could remember the theft.

The judge said he hoped the time served would be a ''wake up call''. Michael Inman