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870 extraction force depends on how hard you operate the gun, but normal operation should toss the empty case at least several feet.
Most 870's will not throw a fired case across the range like many guns will.
It's not necessary to forcefully operate an 870 like you're trying to break the gun.
Test the extractor for free movement.
If necessary, disassemble the extractor and inspect the spring and plunger for distortion, debris, and check the spring tunnel in the bolt for debris or anything that interferes with the spring and plunger's free movement.
Check the fit of the extractor to the barrel. It's possible for an Express barrel to interfere with the fit of a milled extractor with the cut in the barrel, and it may be necessary to relieve the slot slightly to clear the extractor.
Inspect the rear edge of the chamber for any sharp raised edges that might cause a shell to stick. These usually don't look like burrs, just a sharp edge that's turned into the chamber slightly.
Especially with cheap shells this can be a problem.
Check the ejector and ejector spring in the left wall of the receiver. The spring should be present and the ejector should not be chipped or broken.
Check the chamber in the barrel for roughness. If it looks a little rough, put some 0000 steel wool on a used bore brush, put the brush on a cleaning rod, chuck the rod in a drill and polish the chamber by running the drill at medium speed, keeping the brush constantly moving.
You can also polish or clean the bore with this, but make sure any screw-in choke is IN THE BARREL so as not to damage the threads.