How can I make my bullet travel in a straight line without it being effected by gravity?

local Tool = script.Parent;

enabled = true

local spark = Instance.new("Sparkles")
spark.Color = Color3.new("Really red")

function fire(v)

    local vCharacter = Tool.Parent
    local vPlayer = game.Players:playerFromCharacter(vCharacter)

    local missile = Instance.new("Part")


    spark:Clone().Parent = missile

    local spawnPos = vCharacter.PrimaryPart.Position

    local PewPew = Tool.Handle:FindFirstChild("PewPew")

    if (PewPew == nil) then
        PewPew = Instance.new("Sound")
        PewPew.Name = "PewPew"
        PewPew.SoundId = "http://www.roblox.com/asset/?id=88633606"
        PewPew.Parent = Tool.Handle
        PewPew.Volume = 1
    end


    spawnPos  = spawnPos + (v * 6)


    missile.Position = spawnPos
    missile.FormFactor = "Custom"
    missile.Size = Vector3.new(2.5,0.2,0.2)
    missile.Velocity = v * 90
    missile.BrickColor = BrickColor.new("Really red")
    missile.BottomSurface = "Smooth"
    missile.TopSurface = "Smooth"
    missile.Name = "Spark"
    missile.Reflectance = 0
    missile.CanCollide = false 

    local force = Instance.new("BodyForce")
    force.force = Vector3.new(0,98,0)
    force.Parent = missile


    local creator_tag = Instance.new("ObjectValue")
    creator_tag.Value = vPlayer
    creator_tag.Name = "creator"
    creator_tag.Parent = missile

    local new_script = script.Parent.LaserBlast:clone()
    new_script.Disabled = false
    new_script.Parent = missile

    missile.Parent = game.Workspace

    PewPew:Play()

end



function gunUp()
    Tool.GripForward = Vector3.new(0, 0, -1)
    Tool.GripRight = Vector3.new(1, 0, 0)
    Tool.GripUp = Vector3.new(0, 1, 0)
end

function gunOut()
    Tool.GripForward = Vector3.new(0, 0, -1)
    Tool.GripRight = Vector3.new(1, 0, 0)
    Tool.GripUp = Vector3.new(0, 1, 0)
end

function isTurbo(character)
    return character:FindFirstChild("BoltHelm") ~= nil
end


function onActivated()
    if not enabled  then
        return
    end

    enabled = false


    local character = Tool.Parent;
    local humanoid = character.Humanoid
    if humanoid == nil then
        print("Humanoid not found")
        return 
    end

    local targetPos = humanoid.TargetPoint
    local lookAt = (targetPos - character.Head.Position).unit

    local reload = .1
    --if (isTurbo(character)) then
    --  reload = .25
    --  print("turbo")
    --end

    gunUp()
    fire(lookAt)
    wait(reload)
    gunOut()
    wait(reload)

    enabled = true

end

function onEquipped()
    Tool.Handle.EquipSound:play()
end

script.Parent.Activated:connect(onActivated)
script.Parent.Equipped:connect(onEquipped)