Algodoo

It's a little buggy, and the mechanisms would not function in real life, but it's not bad at all! There's really no way to tell whether it fired or not, but it does work nearly flawlessly (with extreme care, though!)

I would recommend increasing sim frequencies and making intricate mechanisms more robust by increasing their density to improve the mechanical accuracy and stability of a scene. Other than that, the quality of a scene comes with practice!

Thank you for the advice, it seems like it's always the little things that kill me