Algodoo

I think you're a little bit confused? The StG44 is a rifle already, and it uses tilting bolt, not roller-delayed
Hell I made one in Algodoo, take a peek if you think it's different:

http://www.algodoo.com/al … p?id=81335

As of the scene itself, you're on the right path, but 5000 Hz??? Lol

You have to use VERY high densities on everything that collides, usually (much) higher than 100 - for example 400 or 500. but try numbers until you find a balance for each thing, for example you can get away with lower densities on the bullet and much lower on the shell. Other things like the killable strip on the bullets can be density 2 as it'll be the same.

this way you can make the springs MUCH stronger (more firerate), and lower the frequency to something bearable (less than 500 Hz if possible), so that you can use simulation speed 1x and not kill everyone else with lag

The trigger group needs a limit for the trigger (i broke the interruptor by dragging the trigger) and one for the interruptor too, and the thruster is too weak to fire when on full auto. but it's functional which is nice