I had a heck of a time getting my extended mag together too. If I ever take it apart again I will drill a small hole through the bottom of the plastic floor plate, after its apart, so a small punch can be inserted to hold the front of the metal plate down in front. I think that would force the little arms in position so it all can slip in place. One hole is not enough to push the metal plate down without the front end popping up and not letting the arms be in the correct position.