I got a 870 and I never put the plug in it. I never used it to hunt yet so I just left it out. I have been thinkin about hunting with it. A plastic rod came with it to stick in the magz tube. I just unscrewed the end cap that holds the barrel on and pushed the rod down in the tube. There was pressure against it from the spring so I had to take my time getting the threads to line up right. In the end of the magz tube the stopper has notches that the cap catches on when theres no plug in the tube. I think they act as a lock mech. But when that plug is in the tube and this causes the end cap to be depressed down into the tube and the notches don't catch the cap. Am I installing this plug right or should I take the tube completely off and put the plug inside the spring so the end stopper notches can lock the cap on...????

I got it if you push down and turn the tube cap 1/4 turn it comes out and you can get to the spring to install the plastic rod...

You got it b4 I could respond.