The Sten 9mm conversion uses the Olympic Arms style upper with World War II Sten submachine gun magazines. They are inexpensive and readily available. These magazines feed ammunition from the center position. Sten magazines do not have a tab to hold the bolt open on the last round.
Adapter required.....
https://hahn-precision.com/ar-15-sten-9mm-adapter/
Buffer recommended for rifles with telescoping stocks.....
https://hahn-precision.com/ar-15-sub-caliber-buffer/
