Framework V1

repeat
    wait()
until game:IsLoaded()

local plr = game.Players.LocalPlayer
local char = plr.Character
local mouse = plr:GetMouse()
local cam = workspace.CurrentCamera

local User = game:GetService("UserInputService")
local Run = game:GetService("RunService")

local RS = game.ReplicatedStorage
local GunModules = RS:WaitForChild("GunModules")
local GunModels = RS:WaitForChild("GunModels")

local Primary = "AK47"
local WeaponInHand
local LArm, RArm
local WeaponData

local aimming = false

local maincf = CFrame.new() --weapon offset of camera
local larmcf = CFrame.new() --left arm offset of weapon
local rarmcf = CFrame.new() --right arm offset of weapon

local aimcf = CFrame.new()

User.MouseIconEnabled = false
plr.CameraMode = Enum.CameraMode.LockFirstPerson

Run.RenderStepped:Connect(function()
    if WeaponInHand and LArm and RArm then --Check if the weapon and arms are loaded
        WeaponInHand:SetPrimaryPartCFrame(
            cam.CFrame
            * maincf
            * aimcf
        )

        LArm:SetPrimaryPartCFrame(
            WeaponInHand.PrimaryPart.CFrame
            * larmcf
        )

        RArm:SetPrimaryPartCFrame(
            WeaponInHand.PrimaryPart.CFrame
            * rarmcf
        )

        if aimming then
            aimcf = aimcf:Lerp(WeaponData.AimCFrame,0.2) --Goal CFrame (lower the number, lower the speed is)
        else
            aimcf = aimcf:Lerp(CFrame.new(), 0.1)
        end
    end
end)

function setup(weapon)
    --setup weapon data module
    WeaponData = require(GunModules:WaitForChild(weapon))

    maincf = WeaponData.MainCFrame
    larmcf = WeaponData.LArmCFrame
    rarmcf = WeaponData.RArmCFrame

    --setup arms to camera
    LArm = RS:WaitForChild("Left Arm"):Clone()
    LArm.PrimaryPart = LArm:WaitForChild("Main")
    LArm.Parent = cam
    for i, part in pairs(LArm:GetChildren()) do
        if part:IsA("BasePart") then
            part.Anchored = true --Make all the parts anchored so it wont fall off
            part.CanCollide = false --make al the parts cant collide so the character wont fly
        end
    end

    RArm = RS:WaitForChild("Right Arm"):Clone()
    RArm.PrimaryPart = RArm:WaitForChild("Main")
    RArm.Parent = cam
    for i, part in pairs(RArm:GetChildren()) do
        if part:IsA("BasePart") then
            part.Anchored = true --Make all the parts anchored so it wont fall off
            part.CanCollide = false --make al the parts cant collide so the character wont fly
        end
    end

    --setup weapon to camera
    WeaponInHand = GunModels:WaitForChild(weapon)
    WeaponInHand.PrimaryPart = WeaponInHand:WaitForChild("Handle")
    WeaponInHand.Parent = cam
    for i, part in pairs(WeaponInHand:GetChildren()) do
        if part:IsA("BasePart")then
            part.Anchored = true --make all th parts anchored so it wont fall off
            part.CanCollide = false --make all the parts can't collide so the charcter won't fly
        end
    end
end

mouse.Button2Down:Connect(function()
    aimming = true
end)

mouse.Button2Up:Connect(function()
    aimming = false
end)


setup(Primary)