A disassembled shotgun found at Pinnacle Reserve led police to the fourth arrest relating to the murder of Bandidos Central West Chapter president Shane De Britt north of Molong in January.

Last month, three men were arrested in Wellington over the same murder and remain before the courts.

Homicide Squad's Detective Chief Inspector Wayne Walpole said the four men were all believed to be part of a rival gang, but wouldn't specify which.

"He was involved in a rival gang. They were all associated with a rival gang," he said.

Detective Chief Inspector Walpole said police received information about the shotgun being located at the Pinnacle Reserve, and while the firearm was still being examined he believed it to be the murder weapon.

"That search .... uncovered a number of parts of a firearm which we believe was the actual murder weapon," he said.

VIDEO: Watch detectives searching The Pinnacle Reserve. Vision: NSW Police Media

"Parts that we located were scattered throughout the reserve, it's fairly thick, overgrown bush there and it was basically thrown into the bushes there."

He said officers conducting the arrest at 9.30am Tuesday had taken a number of items into custody from the Churchill Street residence which were still being analysed.

Detective Chief Inspector Walpole said more arrests were to come.

"I said two weeks ago when we arrested the men at Wellington that the investigation wasn't over and we continue to receive information from various sources and we will be making further arrests in relation to this murder," he said.

Along with a murder charge, the 38-year-old man is expected to be charged with being a member of an illegal organisation and charges relating to firearm possession.

His court date is yet to be set. Investigations under Strike Force Kerrison, which is investigating the murder, are ongoing.