I have been tring to get 1 of Thomspon machines lowered receivers. I have looked everywhere to find the barrel spring,take down button and its spring, and charging handle. I finally gave up and called FNH. To my surprise, you cant enough get these pieces. Even sent me a breakdown so I could ID the pieces I need. Turns out they are part of the receiver assembly and can't be ordered seperately. Man what do we do if a spring ever wears out or something. This is frustrating.