A member of the public called 999 to raise the alarm after they saw the youngsters on Ironwood Avenue on the town’s Grange Estate at about 8.30pm on Saturday evening.
The boys are thought to have been between 10 and 14.
Firearms officers, backed up by a police dog handler, swept the area as well as searching the High Street and town centre but drew a blank.
A Northamptonshire Police spokeswoman said: “A member of the public called the Force Control Room at about 8.30pm and reported they had seen two boys with a suspected firearm.
“An extensive search of the area was carried out,” she said.
“However, there was no trace of the boys and no further calls to the force.
“The local Neighbourhood Policing Team are continuing with enquiries in an attempt to identify the two boys.”