When ever you shoot a gun the bolt flies back and ejects the shell. (whenever you shoot a bullet only the tip is used as a projectile, leaving the shell) and this is not seen in that fit
[spoiler]I'm a gun nut[/spoiler]
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Well seeing as this gif looks like it was from one of the characters imagination. I doubt this part was meant to look very realistic. The guns in the series do have recoil, and the shells do whatever you said they do normally.