What is the best way to make this projectile be rotated the right direction?

When I create a projectile I position its CFrame to be at the tip of the staffs CFrame which I know is the problem because when I shoot the projectile, it goes in the direction of the mouse UnitRay and the tip is not always rotated in that direction. What would be the best way to fix this problem?

local tip = script.Parent.Tip
local player = game:GetService("Players").LocalPlayer
local mouse = player:GetMouse()

local cast = game:GetService("ReplicatedStorage"):WaitForChild("Cast")

cast.OnClientEvent:Connect(function()	
	local p = Instance.new("Part")
	p.Parent = workspace
	p.Anchored = false
	p.BrickColor = BrickColor.new("Really red")
	p.Size = Vector3.new(1,1,3)
	p.CanCollide = false
	p.CFrame = tip.CFrame
	
	game.Debris:AddItem(p, 5)
	
	local bv = Instance.new("BodyVelocity")
	bv.Parent = p
	bv.MaxForce = Vector3.new(math.huge, math.huge, math.huge)
	bv.Velocity = mouse.UnitRay.Direction * 100
end)

If I understood correctly, you want the velocity to be in the right direction of the tip. You can probably use CFrame#lookVector.

bv.Velocity = p.CFrame.lookVector * 100

Wiki:

Vector3 CFrame.LookVector

The forward-direction component of the CFrame’s orientation.