I have spent a day on a shooting range today. It was fantastic, getting ready for the World Shotgun Championship.
There were 2 guys with Remington 870 shotguns. Everything was ok until shotgun of one of the shooters jammed. The fired shell stuck in a barrel of his 870. When he applied force to the forend here is what happened:
The extractor ripped the rim of the shell off! This is the worst case scenario Remington 870 shell jam because there is no chance of taking it out fast and without special tools.
There are several ways to fix this. It is important to unload a shotgun and check that magazine is empty and safety is on. Then you need to disassemble a shotgun and use ramrod to remove the shell.
If situation requires to remove stuck shell fast, you can use ramrod to push stuck shell back with ramrod without disassembling the Remington 870.
Polishing a Remington 870 Chamber will fix this problem and extraction of fired shells will be more reliable.