While the weapons were bought in western Sydney, Assistant Commissioner Denis Clifford told AAP police believed the alleged family-run weapons sales syndicate had also been operating across the lllawarra.

His comments come after raids on a Warilla home, along with properties in Windsor, Greystanes, Londonderry, Castlereagh and St Marys, around 6.15 this morning.

An M1 military assault rifle was seized in the raids, along with 17 other guns.

An undercover detective infiltrated the alleged syndicate in October and bought 13 guns.

The weapons are being examined to see if they were used in any of the hundreds of shootings in Sydney over the past three years

Heavily armed officers from the tactical operations unit arrested a 55-year-old man from Windsor, in Sydney’s northwest on Tuesday.

A brother and sister, aged 45 and 43 respectively, were arrested in Greystanes and Wentworthville in the city’s west.

The trio are due to appear in Sydney courts on Tuesday and Assistant Commissioner Denis Clifford said it would be alleged they were ‘‘significant players’’ in an organised syndicate selling illegal firearms in western Sydney.

‘‘When you look at some of the guns, you shake your head and wonder what that firepower would do if it got into the wrong hands,’’ Mr Clifford said.

‘‘This will no doubt put a significant dent in the organised sale of illegal firearms in western Sydney but we’re sure there’s a lot more out there."

The M1 assault rifle is a military-issued gun and cannot be legally bought by licensed gun owners.

Other guns seized include semi-automatic pistols and shotguns, along with hundreds of bullets.

A woman has been arrested, following a raid on a house in Warilla this morning.

-with AAP.