This kit will allow you to build a blank firing replica of a Thompson M1A1 with simulated full auto fire if you already have an original parts kit. You can also take parts from an original full auto and quickly attach them to this to fire blanks without having to transport a firearm. These parts are designed to work with original mil-spec parts, however minor hand fitting may be required due to inconsistencies or condition of original parts. This is NOT a firearm and is ATF approved. It uses a .46 caliber blank available from Atlantic Wall Blanks. The blanks feed well through original magazines. Receiver is made from high grade steel and comes in a beautiful deep blue finish. This has adjustable tuning. This does not work with semi auto or cheap display gun lowers. If you are unsure about whether it will work with your lower, you can send it to us to check before purchase. Patented design. You will need the following original parts to complete it: