A man has been charged after police allegedly seized 250kg of explosive material and 40 firearms from a rural bush property.

Police allege they found the haul - which included seven pipe bombs, seven improvised explosive devices and a ballistic vest - after raiding a property on Bells Line of Road in Kurrajong, 75km north-west of Sydney, on Wednesday.

NSW Police claim they also seized 77 knives, five electronic stun devices and six firearm silencers.

Simon Clay, 42, was arrested and taken to Windsor Police Station.