Here is my Knex tube fed, shell ejecting BM shotgun. It was fed off tube feeding shell bullets, which were three grey spacers taped together with a white rod on the inside. It fired white rods only 30FT with two bands. It held 5 shell loaded rounds which ejected where a real shotgun would. The way you'd eject the empty shell would be to press the button in pictures 7 & 8, it would automatically load in another shell waiting to be fired. Ram rod powered. Built for engineering creativity, not looks! It was a fantastic little gun.
There are no more pictures, the gun is no longer together.