I have an old Savage 775A shotgun I cleaned it thoroughly and shot 12 rounds of 8 through it but it wont eject the spent shells?

Answer 1

take it to a gun smith and see if they can get the ejector/extractor replaced. Tell him/her what's wrong and they should be able to fix it. Also, try High brass and low brass as some shotguns are -very- picky about the size of the brass you use.

The main and most likely reason for not ejecting is that you probably have the friction/governor ring set up for heavy loads. The setting needs to be changed for heavy and light loads, exactly like a Remington model 11 or Browning A5.