Semi-automatic airsoft gun, very simple

[hectmarr]

Playing with a syringe, a small spring a 5/2 and a bb of 6mm, plus a couple of hours in the afternoon. The result is not impressive but yes, very fun to do and shoot. Shoot with 80 psi :bounce:
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[jackssmirkingrevenge]

Very nice! Is it a blow forward valve?

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[hectmarr]

It is a common valve, of which they have for one side the two escapes and the supply of compressed air, and for the opposite side, the two exits. Too bad that support low pressure, up to 120 psi, but it is enough for this application. I need an exterior fairing with the look of a modern weapon, made of fiberglass or something similar.
Your design is excellent, and very simple. I had seen it and I like it.
He is connected in this way, he had already published it.

[FerdBlu]

How do the BBs get into the Barrel? Via a sliding magazine over the barrel?

[hectmarr]

It was more or less like that, like in the drawing.

[Dembouz921]

If you keep pulling the air pistol trigger does the blow forward valve in the syringe stays open? If so I think by restricting the blowgun airflow you could make it fire fully automatic. As the blowvalve in the syringe releases air in the barrel, air is still coming from the blowgun but with a relatively low airflow so the piston have time to close enough to load an other bb then pressure builds up again and the piston goes forward again. I'm not sure it will works good because with a limited air flow you may have a slow rof.

[jackssmirkingrevenge]

If you keep pulling the air pistol trigger does the blow forward valve in the syringe stays open? If so I think by restricting the blowgun airflow you could make it fire fully automatic.

Yes, I had hoped it would work in full auto (here is a development thread) but I could never get it to cycle properly, it needs the airflow to be cut off in order to reset properly.

Some theory for an improved design.



Similar idea but incorporating a pop-off element to increase power:



There are better ways to go about it however, a blow forward valve uses a lot of energy to cycle the mechanism and there is a lot of dead volume, so it's not the most efficient solution.