JStark1809 notes in addtion to Incarbonites instructions: If you want to use a JG/Golden Eagle M4 fire control group in your FGC-9 build, you will need to make sure that you are using the following components with it. Following parts from your airsoft fire control group: - Trigger - Hammer - Disconnector Components for/from actual AR-15 rifles: - Trigger spring - Hammer spring - Disconnector spring - Fire selector - Fire selector detent - Fire selector detent spring You can buy the AR-15 components on AliExpress. You can find the parts in parts kits that often are listed as: "AR15 Lower Parts Kit 223 / 5.56" "Kit All Lower Pins, Springs and Detents .223/5.56 AR15 Parts" Example listing: https://www.aliexpress.com/item/33008262340.html