I have a question about my 870 express. My 870 express doesn't have a magazine extension. And the magazine cap locks down with the teeth on the plastic magazine spring cap. I want to install a Wilson Combat magazine tube extension and I know I have to drill out the two little protrusions on my magazine tube. So here is my question. I noticed the mounting ring on my barrel has the little hole in it for the magazine cap detent and detent spring. I know I can buy both the magazine detent #F17451 and magazine detent spring #16791. How does the magazine detent spring and magazine detent install into the little hole in the barrel mounting ring? Does it need pressed in or does it just slip in?