The boy, 10, has been charged with common assault over the gun incident, which occurred on the same day he allegedly threatened a video store employee with the gun before escaping with cash.

Police will allege the boy entered the Harvey Norman store in Muswellbrook Fair on September 22, aimed the pistol at the woman and pulled the trigger, causing a cap to pop.

It will also be alleged the boy walked into the Network Video store on the same day and pulled out the replica pistol before threatening an 18-year-old female worker.

She handed over some cash and the boy left with several other boys waiting outside.

He was arrested last Friday and later charged with robbery while armed with an offensive weapon and common assault.

The armed robbery charge is too serious for the boy to be dealt with under the controversial Young Offenders Act and he will have to front a judge.

The boy, who cannot be identified, was granted bail on strict conditions to appear in Muswellbrook Children's Court next month.

He is believed to be one of the youngest people to be charged in NSW with armed robbery, which carries a maximum jail term of 25 years.

The bail conditions include a curfew between 6pm and 8am, that the boy not leave his home unless accompanied by a responsible adult and that he not associate with another boy.

Hunter Valley detectives are continuing to investigate the armed robbery and further arrests may be made.