The owners of Lark Hill Winery hoped the bullet casings could be linked to a registered firearm to help identify whoever was responsible for leaving piles of building waste and garbage near an entrance to theor property.

Co-owner and winemaker Chris Carpenter said the garbage included building waste, insulation, an old trampoline and a bagful of springs.

"It looks like someone's emptied an old garage," he said.

He found a several dozen brass casings in the side pocket of a bag among the trash.

"I was looking through the rubbish trying to find some ID," he said.

"That's probably the closest we'll get, the number of people with a nine-millimetre handgun in Bungendore probably isn't high.

"We're just hoping there was someone who saw a ute loaded up with rubbish who was driving past at the time, or someone who knows someone with that calibre handgun who threw out their trampoline."

Police told Mr Carpenter the spent cartridges were not a significant concern as they did not contain any ammunition.

But they said dumping them was an unusual thing to do as such cartridges could be reused.