Bullet only goes on Z axis, not Z axis relevant to the gun?

I made a script, when you click, it shoots a bullet. Unfortunately, the bullet only goes on the Z axis, not the Z axis relevant to the gun! Why is that happening? Here is my script

wait(1)
script.Parent.Equipped:connect(function(mouse)
    mouse.Button1Down:connect(function()
--  local animation = script.Slash
--  local plyr = script.Parent.Parent.Name
--  local char = workspace:FindFirstChild(plyr)
--  local anim = char.Humanoid:LoadAnimation(animation)
--  anim:Play()
    local bullet = Instance.new("Part")
    bullet.FormFactor = "Custom"
    bullet.Size = Vector3.new(0.5,0.2,0.2)
    bullet.BrickColor = BrickColor.new("Toothpaste")
    bullet.BackSurface = "SmoothNoOutlines"
    bullet.BottomSurface = "SmoothNoOutlines"
    bullet.FrontSurface = "SmoothNoOutlines"
    bullet.LeftSurface = "SmoothNoOutlines"
    bullet.RightSurface = "SmoothNoOutlines"
    bullet.TopSurface = "SmoothNoOutlines"
    bullet.Velocity = Vector3.new(0,0,100)
    bullet.Parent = workspace
    bullet.Position = script.Parent.Handle.Position
    bullet.Transparency = 0
    bullet.CanCollide = true
    --local speed = script.Speed:clone()
    --speed.Parent = bullet
    local damage = script.DamageScript:clone()
    damage.Parent = bullet
    print("HALLAAA")
    end)
end)

Please help!!! Thank you!!!