How to make a Lego shooting mechanism

Instructions can be found here: https://rebrickable.com/users/kueden/mocs/

I was asked to provide a simple description of how to build the Lego Technic shooting mechanism behind the various guns and cannons published in the last two years. This is a very basic explanation of the mechanism used for storing the mechanical energy and releasing it.
It is based on the yellow rubber belts (Lego part 85546). Instead steel springs can be used.
The following performance is obtained depending on the number of rubber belts installed:

1 rubber belt: muzzle velocity 5 m/s, range of fire: 2.6 m
2 rubber belts: muzzle velocity 6.1 m/s, range of fire: 3.8 m
3 rubber belts or steel springs: muzzle velocity 6.9 m/s, range of fire: 4.8 m

While the actual shooting mechanism is identical in all the guns, the ammunition feeding system varies. The following three principles are used for feeding:
- Rigid belt
- Revolver
- Magazine

The feeding is accomplished either by:
- The gravity
- The motor
- The recoil of the gun

The control of the feeding is achieved through one or a combination of the following actions
- Shooting action
- Motor rotation
- Recoil of the gun

You find the various amunition feeding systems here: https://rebrickable.com/users/kueden/mocs/

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