How to load guns for team?

You could make a few folders in a service named after whatever teams you have and insert whatever tools you wish to award to players on the corresponding team.

local armory = "path so instance/service containing team folders"

local function setTools( player, team )
  local backpack = player.Backpack
  local starterGear = player.StarterGear
  
  starterGear:ClearAllChildren();
  backpack:ClearAllChildren();
  
  for _, child in next, armory:GetChildren() do
    if player[property] == BrickColor.new(child.Name) then
    
      for _, tool in next, child:GetChildren() do
      tool:Clone().Parent = starterGear
      tool:Clone().Parent = backpack
      end
    end
  end
end

game.Players.PlayerAdded:connect(function( player )
  player.Changed:connect(function( property )
    if property == "TeamColor" then
     setTools( player, player[property] )
    end
  end
end)