i think i know what is wrong, i picked up the same gun at an auction and found the same thing. mine will eject the shell from the tube but it will jam and not proceed into the chamber, i fixed it yesterday after a healthy bout of swearing, but i noticed the arm that holds the shells back in the tube has a tine little spring that allows it to fall back in place one a shell has been cycled. if you hold the gun muzzel up and look into where you load it you'll see the arm that i am talking about on the right side, you should see a little spring near the bottom of the opening holding the arm up, or the hole that it goes into. if this is missing i'm sure a local gunsmith will have something that'll work, if not i used a flint spring from a bic lighter and just cut.
hope this helps
