M1 Super 90 Magazine

[sherwoodshr]

I have a H&K Montefeltro Super 90 12 guage shotgun. The magazine is meant to hold 2 3" shells. During a recent duck hunting trip I attempted to reload and only one round would go into the magazine. The Owner's Manual for the gun does not show the Montefeltro magazine end. The pictured end cap is removable. My magazine, however, has a threaded hollow rod. I can hear something loose in the tube but do not see how to remove the magazine's end to replace/repair the shell limiting rod. When I called Benelli for help I was told to hold the gun so the threaded tube is pointing downward and the rod should fall out. This does not work. I was told there is no way to open the magazine to get at the problem. Any suggestions??