How do I cast a ray towards a specified part?

Sorry for spamming the site but I'm close to where I want this game to be at the moment. I want to test if the gun is clipping through a wall. The way I want to go about this is casting a ray from the tip of the gun towards the head of the character. If it intersects a part (so if the gun is clipping something) it won't fire the gun. This is what I tried for the sake of trying (pls dont bully me JesseSong)

function CheckCollision()
	local rayOrigin = FirePointObject.Position
	local rayDirection = script.Parent.Parent.Head
	
	local raycastParams = RaycastParams.new()
	raycastParams.FilterDescendantsInstances = {script.Parent} -- gun
	raycastParams.FilterType = Enum.RaycastFilterType.Blacklist
	local raycastResult = workspace:Raycast(rayOrigin, rayDirection, raycastParams)
	if raycastResult then 
		return
	end
end

I get an error saying Unable to cast Instance to Vector3 so I probably got the rayDirection wrong. Any help is appreciated.