Don't have a Benelli so can't answer all. Slight rust on rag is that slight rust. You need to look at where you are storing. May be too much humidity. Usually hunting guns would be limited in number of shells you can hold in mag. You need to check on that. Can end up in trouble with ranger. For HD is different. There is extended competition mag tube for M1-Practical and Super Black Eagle Models. Call Benelli USA (301)283-6981. Also have web site:
www.benelliusa.com