Police believe they have found the gun a 30-year-old man allegedly used to kill his father and uncle on a central Victorian farm.
Ross Streeter, of Bendigo, appeared in the Melbourne Magistrates Court on Tuesday charged with their murders.
Detective Glenn Boxhall told the court a police search on Monday afternoon had recovered a firearm, believed to be the murder weapon.
He said Streeter went to the family farm in Natte Yallock and shot his uncle John Streeter on Thursday.
"He then left the area and returned shortly after and shot his father Doug Streeter and returned back to the Bendigo area," Detective Boxhall said.
He said police needed time to further search the 1600-hectare farm and analyse forensic items, DNA, phone records and text messages.
Police also had a witness who, although not with the accused during the alleged murders, was with him around that time.
There were also a number of people involved with the family's complex financial arrangements, which police needed to examine, including wills and accounts.
Detective Boxhall said Streeter had not made any comment when interviewed about the murders.
Streeter appeared in court cradling an injured left arm and his lawyer requested he see a medical officer for the injury.
He did not apply for bail and was remanded for a committal mention on June 25.