The gun seized by police.

The gun seized by police. Photo: @Barnsy_Lisa/Radio 6PR

An illegally manufactured sub-machine gun capable of firing 15 shots before needing reloading has been seized from a bikie clubhouse by West Australian police.

Police searched the Myaree clubhouse of the bikie gang Rock Machine this week as part of Operation Unification targeting illicit firearms, and found the gun unsecured in a black bag and loaded with two rounds of ammunition.

Several people were present, so police are still trying to work out who the gun belongs to. Charges are yet to be laid.

Inspector Dale Davies of the licensing enforcement division says it's concerning that blueprints for the firearm are readily available on the internet.

"We are finding more of these weapons, which is obviously of great concern to us," he said.

Police also seized a Ruger A.M.A. bolt repeater rifle and 800 rounds of ammunition from a home in Waikiki, all unsecured, on Friday.

A 57-year-old man at the residence has been charged with failing to safe keep a firearm and ammunition.