Your list of probably caused doesn't explain mine with a Escort Extrema Magnum Waterfowl shotgun. From two years ago, the first time I shot it until yesterday, the gun will not eject the shell all the way on every load. I though I needed to break it in. 2 3/4, 3", 3 1/2" all don't eject all the way. 2 3/4" and 3" have this issue about every third shot. The 3 1/2" won't even eject 100% of the time. The next shell comes out of the magazine and I am constantly trying to get one empty shell out of the chamber/receiver with another one in the chamber/receiver with it. I've clean it. I've studied it. I use quality shotgun shells (all steel shot). Improve Cylinder choke. This problem started when it was brand spanking new and only got worse. Very unhappy with the shotgun. My Benelli SBEII only had this issue rarely with only clay pigeon rounds. If you only put one round in, it ejects perfectly every time. Manually eject the shells pulling the bolt fast, works perfectly. Shoot it! Problem.
