Police raided a house in Wetherill Park, in Sydney's southwest, yesterday.
They found three shotguns, three rifles and a large amount of ammunition along with a small amount of cocaine and steroids.
Police also seized several pieces of Hells Angels clothing.
A 21-year-old man was arrested and taken to Wetherill Park Police Station where he was interviewed before being released.
Police expect charges to be laid after forensic testing is done.
"It will be further alleged the man is a member of the outlaw motorcycle gang," police said in a statement today.
The arrest relates to the June 30 shooting in the western Sydney suburb of Merrylands and the shooting in the eastern suburb of Dover Heights.
Police had been called to a home in Holdsworth Street, Merrylands after residents reportedly heard gun blasts.
They arrived to find the front of the home riddled with bullet holes although a woman, 47, and a boy, 7, escaped injury.
Less than 24 hours later, forensic officers went to a home in Dover Heights after bullet casings were found on the footpath.
Police believe the two houses were shot at on the same night.
Strike Force Bairstowe, comprising detectives from Middle Eastern Organised Crime Squad, was formed to investigate both shootings.