870 Ejecting into Self

[Sven]

My 870 will once in a while take an empty shell back into the chamber, reversed - happens when loading one and shooting one shell. Any ideas?

 

[dfariswheel]

Check the ejector assembly on the left sidewall of the receiver to be sure everything is Ok.

Disassemble and check/clean the extractor, plunger, spring, and the extractor tunnel in the bolt.
Check for free movement.

I've seen several 870's extractor assemblies with factory grit embedded in the spring tunnel, interfering with the spring. One was so bad, it needed polishing of the tunnel.