Algodoo

A sub machine gun with an open bolt design, a folding stock and an optional grip and red dot sight. The magazine can hold 30 rounds, but the scene is less laggy and the gun works better when you only put in 5 or 10 rounds.

On my computer, when I put 5 rounds in the magazine, the gun worked flawlessly nearly every time, and shot quite fast. The only thing that goes wrong is the bolt won't go back far enough, but that happens rarely with a 5 round mag.

On scene start, the magazine is loaded with 5 rounds, and in the gun's reciever.

Instructions:

To load a magazine:

Copy as many rounds as you want, and drag them into a magazine. Be carefull, as the rounds will pop out easily.

To fire the gun:

When you have a magazine loaded, slide it upwards (gently) into the reciever.
Pull the dark gray circle to the left until it is all the way back, and release.
Hold Enter/Return or pull the trigger to fire.
When the gun stops firing, take the magazine out and repeat.

If the gun jams, cycle the bolt, and it should fix the jam.

This gun requires algodoo to run at a frequency of 500Hz. Before you un-pause the scene, look at the sim-info window, or open the console by tapping tilde (~) and type in sim.frequency.

If the sim.frequency is anything other than 500, type into the console: sim.frequency = 500. This gun is designed for 500Hz, so it may not work at even 450Hz or 550Hz, even though they're very close.

UPDATE:

All of the unnecessary things that are just for looks are grouped together, and you can now press the 1 and 2 keys together at the same time (not numpad) to delete them all. ( of course you can just select them and delete them manually, but where's the fun in that?)
If the gun does not work properly, try deleting all of the 'just for looks' crap, and it should work perfectly.