Algodoo

Now that's pretty original. Great work.

Its hard to tell since I'm working on them over long periods of time, very rarely exceeding 1 hour a day.
I guess it takes me around 4 to 8 hours for more complex one.

Very nice. Locking system is pretty smooth and strong, spent case ejection also works fine. There is one problem however - its very easy to slamfire this weapon, there is no firing pin blocking mechanism, so its free to move forward when the bolt is closed quickly, and this causes accidental discharges pretty often. This problem is very easy to fix, so I won't take off any points for that.

9/10

I don't mind at all, that's what concepts are for.
Maybe you'll find a way to improve this system.

Increasing the size and mass of objects usually helps, also using only basic shapes for moving parts (circles and rectangles) improves their collisions. Look at this scene for example - I had problems with spent case extraction (extractor was jumping over the rim of the cartridge because of the low sim frequency, so I've made the extractor hook and casing rim much thicker (thick rim is invisible).

Care to explain why?

Not really, but i think it wouldn't be that hard to do. Might be a bit more unstable with use of recoil only.

I work on way too many things at once, even now I have like 6 or 7 unfinished projects in algodoo only.