M4 failure to feed last round

[Super M4]

Benelli M4 shooting 2 3/4 " shells. I have tried bird to buck shot and still the last round is getting stuck in the tube. It begins to feed out and gets stuck 1/2 way out the tube and 1/2 on the shell carrier. It's a factory mag tube spring but the full length tube. I've tried it with the factory follower and a Brownells follower, still the same problem. The gun is only about 4 months old. Maybe i need a new mag tube spring? Are all 12 ga tube springs the same diameter and just in different lengths? Can I buy another factory M4 spring direct from Benelli?

[bauerdb]

http://www.e-gunparts.com

[d]

I would try pulling the spring a little to stretch it, perhapse a pinch of graphite behind the follower then shaken out. The long tube spring has much more power but decresses tube capacity to five.