I´ve got pictures somewhere of workers at the Royal Germanicon Spandau Armoury inspecting rifle barrels visually and then using a hammer to straighten those that were bent. And I once saw a film of a Kalashnikov factory where the barrels were cut to length off a very large drum on which the material had been delivered. Why not try and straighten your No 5 barrel using pressure between wooden blocks in a vise and inspect it against a strong light between each attempt. It might even shoot quite well. Don´t think you´ve got much to lose.