I found a surprising difference in bolt-action gun design called "A-Bolt" or something like that. Well, it's basically just a straight pull and movable lever instead of the usual rotation cylinder. It's exactly the same design I created for my legofied model and I think it's the only way you can get it to work with Lego. I took the time to break the long time I wasn't working on it and did some nice progress. So far, the most difficult bolt part seems to work reliable. Now I need an equally reliable lever to lock the breech and prevent the bolt from moving around too free. I'm not sure whether to go for pure weight-based locking or some other snap lock to keep it also safe when shooting from different gun body rotations. However, I rather prefer a strong locking I can also apply to other designs. I know Lego can get loose over time and usage, it is no solution to rely on weight and simple blocking.