just purchased a sp350,and took the limiter out so it holds 5+1;but not sure if magazine tube unscrews.do the tubes swap out to work on my model;or do you make an extension?i`am a new shotgun owner,so excuse me.also,called benelli about the skeletonized m4 buttstock and they said they only sell to law enforcement or military!is this because it is not a u.s. compliant part?there are tons of aftermarket m4 stocks for other shotguns.thanks for your help!bob