Algodoo

imo Algodoo not having pressure simulation makes it easier to make guns. Just do this:

Use 200 Hz or more: go to the ear in the upper left corner, then Simulation, and change the frequency slider to 200 or 300

Use more density on everything: use 50 or 100 on every object even if everything seems too heavy. this improves collisions a lot

Use the conventional spring round system: download any gun, take a round and use the ALT key to select individual objects from the round, then hold SHIFT and move the mousewheel up to move the object back, and you'll see how they work

this looks cool

yep that was super cool