GyverGun is Arduino based full-auto airsoft rifle made of very common components and materials. It is capable to shoot 2 steel 4.5 mm BB balls per second with muzzle energy of about 3 Joules. Compressed air is controlled by solenoid electromagnetic valve (truck horn), reloading mechanism is servo. GyverGun has safety switch and fire mode switch (semi-auto and full-auto).
Scope is handmade too, just old binoculars with lens modification, you can watch a video about how to make it here
It's first version of handmade pneumatic full-auto rifle, there will be some update in this year (10 shots per minute bolt =)
Watch a video about GyverGun, there are more detailed instructions there.
Air tank is made of montage foam cylinder with plastic cap (foam for foam gun). It is very important! Empty the cylinder and let all gas go away. Then get rid of all valve parts (just drill it). Take 1/2" fiting and make a thread in plastic cap. Use burner to heat fiting and "melt" the thread. Then use epoxy to fix fiting in cap. So you need a cylinder with 1/2" and 1/8" outputs.
This project is based on solenoid electromagnetic valve (truck horn part) from Aliexpress. It has 1/8" input and 1/4" output, can control compressed air at 15-17 bar. You can find all links on project components here, on project's GitHub page.
Make a guiding rod (nail and pen core) and connecting rod between servo and bold (I used clip). Also make ball feed system (cold weld and PVC tube). Watch a video to see how it works.