Detectives investigating the murder of Rhys Jones believe they have found the gun used to kill the 11-year-old.
Rhys was shot dead as he walked across a pub car park in Croxteth Park, Liverpool, six months ago.
Since then Merseyside Police officers have taken 108 guns off the streets, one of which they believe to be the murder weapon.
Detectives also believe they have identified the exact make of bicycle used by the gunman.
Forensic tests are continuing on the weapon, although police have not revealed what kind of firearm it is.
Although the gun was found some time ago, police have released the information in the week which marks six months since Rhys's murder.
Det Supt Dave Kelly, leading the inquiry, was particularly keen to trace anyone who saw the gunman on a silver Specialized Hard Rock mountain bike on the night of the killing.
Police are now trying to trace this mountain bike
A photograph of the bike - which had a silver frame, black forks and black seat - has also been released.
Mr Kelly said: "I am appealing to anyone who may have seen anyone riding this type of bike in the area following Rhys's murder to contact us.
"I am also appealing to anyone who may know where this bike is now to come forward."
Police believe the bike was left next to another one on a football playing field on Parkview Road, Croxteth, at about 2030 GMT on the night of the murder.
In the six months since Rhys was shot dead, 20 people have been arrested as part of the inquiry - 17 of them on suspicion of murder.
Four remain on police bail while a number are now being treated as witnesses. Two were bailed after being questioned on suspicion of firearms offences and one person was held on suspicion of helping an offender.
Mr Kelly said he was aware about speculation in the community about the killer's identity, but said detectives would be dealing with evidence rather than rumour.
"We have a very clear strategy for this investigation, and we're determined to leave no stone unturned," the detective said.
"We're confident with the advancements we're making in the investigation, and that we will be able to progress towards charges and a successful prosecution, the timescale for which will be governed by the evidence."
In a statement released through Merseyside Police, Rhys's parents Stephen and Melanie Jones said they were pleased with progress in the investigation.
"No parent should ever have to go through what we are going through. Our lives will never be the same," they said.
"Six months on and our world has been turned upside down and all we want is justice for our son."
Rhys was hit by a bullet in the car park of the Fir Tree pub in Croxteth Park on 22 August 2007 and died at the scene. The shot was fired by a youth on a mountain bike.
The 11-year-old had been walking home from football practice and police believe he was the innocent victim of a gangland feud and the killer had another target.