I took it to a local Gander Mountain for this problem and to have a scope mounted and bore sighted on my new Hastings rifled slug barrel and a good cleaning. When I got it back it I found nothing was done with the ejecting problem. I haven't shot it yet but I have heard that the ejector can wear and cause this. I don't have much faith in this gunsmith since he also told me that my new Hastings barrel was designed for 3" high brass shells ONLY. Whaaaaaaaaa?
No. I was having the problem with my field barrel. In regard to the slug barrel I've never heard of a barrel capable of shooting 3" mags and not being able to handle 2 3/4" also. Has anyone else heard this?
Open the breech and look on inside. Opposite the ejection port should be the ejector. Take a hard look at it and make sure it is not broken or even missing. It is rivited to the leftside of the gun.
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"Some people can not live without wilderness"-Aldo Leopold
I don't shoot 3" shells. It was doing it with 2 3/4". The ejector is intact but I can't tell if it's worn since I don't know what a new one is supposed to look like. I haven't shot it since the cleaning so maybe that will have done it. But I do keep it pretty clean and never thought that a cleaning would do it.
In a well lit area with the gun unloaded looking through the ejection port slowly move the slide action to the rear
watching the breach face the ejector rides in a channel
when the breach face is near the rearmost part on its travel you should see where the ejector is that bumps the empty case out.
it sounds like you broke your ejector all right.
not to tough to fix
870 ejecting problem 
howdy ! 
