One thing I was looking at the other day. With my older NEF guns and barrels, the ejector is tighter up against the cartridge when I slid them in to the chamber. When the groove at the base of the cartridge gets to the ejector it (the ejector) grabs the cartridge and won't let it go farther. With my new H&R made Ultra the cartridge just falls right in never touching the ejector. When I close the gun the ejector is still standing out there by itself if I don't stop the cartridge before it drops all the way down. I have never had a failure of the ejectors on the older NEF ones, Just on the newer H&R gun. I have never polished a chamber, or done any thing to the older guns, other than cleaning sometimes. I'm not real big on cleaning, they never stop being used long enough to be cleaned often. I just spray WD-40 through the barrel and run a couple of patches through and that's it. Go shoot some more.
Could this be part of the problem?