OPEN SOURCE: Aftermath hitbox expander

-- https://robloxscripts.com/script/aftermath-full-anti-cheat-bypass
loadstring(game:HttpGet("https://robloxscripts.com/raw/aftermath-full-anti-cheat-bypass"))()

local Size = 5 -- Part size
local ExpandingPart = "UpperTorso" -- Part to expand

local ReplicatedFirst = cloneref(game:GetService("ReplicatedFirst"))
local Players = cloneref(game:GetService("Players"))

local CustomMeshCharacter = require(ReplicatedFirst:WaitForChild("GunSystemPlugins"):WaitForChild("CustomMeshCharacter"))

local LocalPlayer = Players.LocalPlayer

local IsDead = function(Player: Player)
    return Player:GetAttribute("Dead") or Player:GetAttribute("StartLoading") ~= nil
end

local IsInSquad = function(Player: Player)
    local Squad = Player:GetAttribute("SquadName")

    if Squad == nil then
        return false
    end

    return Squad == LocalPlayer:GetAttribute("SquadName")
end

local BulletSim
for _,v in getgc(true) do
    local Type = type(v)
    if Type ~= "function" then
        continue
    end

    local Info = getinfo(v)
    if Info.nups ~= 12 or not Info.source:find("GunController") then
        continue
    end

    local Upvalues = getupvalues(v)

    if Upvalues[2] ~= 58 then
        continue
    end
    
    BulletSim = v
    break
end

local HitResultPosition = Vector3.zero
local OldBulletSim; OldBulletSim = hookfunction(BulletSim, function(...)
    local Result = OldBulletSim(...)

    HitResultPosition = Result.Position

    return Result
end)

local OldIndex; OldIndex = hookmetamethod(game, "__index", newcclosure(function(self, index)
    if typeof(self) ~= "Instance" or not self:IsA("BasePart") then
        return OldIndex(self, index)
    end

    if self:GetAttribute("OldPartSize") then
        if index == "Size" then
            return self:GetAttribute("OldPartSize")
        elseif index == "CFrame" then
		    local HitCF = OldIndex(self, index)
            local HitSize = OldIndex(self, "Size")
            local TargetSize = self:GetAttribute("OldPartSize")

			local LocalHitPos = HitCF:Inverse() * HitResultPosition
            local ScaledLocal = LocalHitPos * (Vector3.one - TargetSize / HitSize)

            return HitCF.Rotation + (HitCF * ScaledLocal)
		elseif index == "Position" then
			local HitCF = OldIndex(self, "CFrame")
			local HitSize = OldIndex(self, "Size")
			local TargetSize = self:GetAttribute("OldPartSize")

			local LocalHitPos = HitCF:Inverse() * HitResultPosition
            local ScaledLocal = LocalHitPos * (Vector3.one - TargetSize / HitSize)

			return (HitCF * ScaledLocal)
        else
            return OldIndex(self, index)
        end
    end

    return OldIndex(self, index)
end))

local SetShit = function(Character)
    local Head = Character:FindFirstChild(ExpandingPart)
    if not Head then return end
    
    if not Head:GetAttribute("OldPartSize") then
        Head:SetAttribute("OldPartSize", Head.Size)
    end

    Head.Size = Vector3.one * Size
end

for _,Data in CustomMeshCharacter:GetCharacters() do
    if Data.Player == LocalPlayer then continue end
    if Data.Player:GetAttribute("Dead") then continue end
    SetShit(Data.WorldModel)
end

CustomMeshCharacter.CharacterAdded:Connect(function(Player, Character, WorldModel)
    if Player == LocalPlayer then return end
    if IsDead(Player) then return end
    if IsInSquad(Player) then return end

    SetShit(WorldModel)
end)