Okay, so I called Benelli and told them about my problem. The woman that I spoke with on the phone seemed to understand. She sent me a new magazine tube spring and a new spring retaining ring and now the M1 is back on track.
I really wanted to add that Benelli really came through for me here. I even asked for a part that wasn't realated to my problem and they sent it without any question. My M1 is probably 15 year old and they were willing to take care of everything. My next shotgun will be a Benelli for sure!