So i haven't been able to shoot my new 870 hd, because i can't figure out how to take it apart and clean it. Its the 870 with the 18 inch barrel and +2 extension. I think im missing something in my manual, because the manual is for the normal ones and says nothing about the HD model. The magazine cap won't screw off...its impossible. Any tips on what do would be greatly appreciate...ive searched the net and can't find a thing.