Pull the plug unload, unscrew the barrel nut (the one that holds the barrel on), use a screwdriver to gently pry out the steel insert (from inside the magazine tube) Be careful as the spring will jump out and dot your eye. Plug will come out with the spring. Replace the spring, compress and reinstall the insert (you can use a screwdriver handle to gently tap it into position) replace the barrel nut, good to go.
Mine must be different since you don't have to pry anything. Remove the cap. Push in on the piece in there to clear the indentations, rotate 45 degrees, and then it will come out, under spring pressure. -Bidah
