I hope for your sake when you built this sten you used a tube that was undersized and will not take the full auto bolt.You cannot legally build a open bolt anything. To make a sten semi auto you must use a undersize tube and a bolt with a unfixed firing pin. To do otherwise is looking for a sure ticket to the slammer for about 10 years and remember there is no time off for good behavor.Ten years means just that ten years.