Algodoo

I found a few serious issues with this scene. While trying to load and then fire the gun, I was wondering why everything was moving in slow motion! While checking a few things, I see that you had set the sim frequency to 12000 Hz. Very bad practice for numerous reasons! For one, many low-end computers cannot handle such a fast sim frequency. For another, the faster the sim frequency, the slower that the scene will appear to run (that's why it moves so slowly). A more reasonable sim frequency would be between 200 and 400 Hz. If your guns cannot operate in that sim frequency range, then you need to do things differently until they do work! Others have posted excellent gun mechanisms that operate just fine at the lower range of sim frequency.

@Xray If the buit is resized and larger then lower frequency is required