Kofi Nti, 21, would spend six months in jail should he fail to pay the fine.
He was charged with unlawful possession of firearm and pleaded guilty to the offence.
Police Chief Inspector Nana Boamah told the court that he was arrested on April 13, 2015, based upon a tip-off.
The police received information that the convict together with three other persons were preparing to go on robbery operation at Dadieso, a suburb of Mampong, and moved quickly to stop them before they could strike.
Nti was found with the gun and 28 pieces of live ammunition, and he was seized.
By C. M. Boaten, GNA