I have two 12 gauges. One wouldn't even start to eject. I totally disassembled and it was caked internally with soot and crud. After cleaning, oiling, and properly adjusting the spring/friction ring setup, it would eject but not cycle. So, after some reading online, I found that a VERY light coat oil (like wipe some on and wipe off with a clean cloth) on the magazine tube allows the barrel to move more freely to eject the shells. If you put too heavy of a coat it can be too much recoil and too much force on the action. You want it to be just enough to cycle. No more.
Fightin Texas Aggie Class of 2009