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Need help with multi shot airsoft gun.

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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Need help with multi shot airsoft gun.

Unread postAuthor: Wallies » Sun Feb 26, 2017 11:01 am

How to make a diy airsoft more air efficent
I've been looking into building an airsoft gun as my first project ever since mine , a 400 fps M14, broke.
Im hoping to use a HPA portable gun-mounted resevoir to fire 0.4 gram bbs at 400-500fps and that the gun is semi-auto and uses a magazine(want to build my own but any airsoft compatibility mods are welcome)

I am planning on using a piston QEV that is piloted by a 3/2 dcv( either connected to another smaller resevoir or the main one using another regulator)or a blowgun.
I plan on using a variable scuba pressure regulator to have a constant fps, which will be between 80-120 psi(similar to normal HPA guns)


the only problem is that I can't seem to find any designs that allow for much more than 12 shots from the reservoir( I'm probably looking in the wrong places) I'm not too worried about ROF ( 1 shot a second is fine) but I would like some general tips on how to minimize air usage per shot while reaching the same fps consistently by mimicking airsoft pressures.

Also because I'm going to be in the field I need to find a way of refilling. I do have access to scuba tanks but I'd much rather prefer a handpump but I dont know if it is feasible.

Lastly I want use a airsoft barrel(aug madbul 6.01x509mm to be specific) from my old gun and either a diy hopup or one from the shop but I don't have any idea as how I can mount it. Any input or critism is greately appreciated as all parts of the design are still far from reality. (Sorry for long post)
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Re: Need help with multi shot airsoft gun.

Unread postAuthor: wyz2285 » Mon Feb 27, 2017 8:24 am

Did this a while back
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Re: Need help with multi shot airsoft gun.

Unread postAuthor: mark.f » Mon Feb 27, 2017 7:18 pm

In general you are going to need a high pressure reservoir and a lower pressure "chamber" and a way to only allow a controlled volume of air from the reservoir (ideally minimal) to get good efficiency.

Most air guns use a hammer valve for this reason, because they can be built to accomplish both tasks easily (regulating air in the "chamber" of the valve to a fraction of the reservoir pressure, and only allowing a certain volume out the barrel when actuated instead of relying on i.e. valve stem inertia vs. hammer, etc.

If you're using a Q.E.V., you need a way to pilot it controllably. Other members on this forum simply pilot them with a hammer valve to achieve multi-shot with a reservoir which may or may not be regulated. You could also use a direct-acting solenoid and a monostable multivibrator or microcontroller.

However, I think you would be better served building a hammer valve; either a simple one, to pilot the Q.E.V., or a more complex one as the main valve to handle the other points. Even a simple hammer valve can be used for the main valve and achieve moderate efficiency without the ability to trap air in a "chamber" or regulate it. Semi/full auto can be handled with a gearbox like most airsoft guns or a solenoid "hammer" and a large battery pack.

In short, just build a hammer valve. :D The outlet flow requirements for a valve in an airsoft gun are moderate and are more suited to a hammer valve in the first place, with Q.E.V.'s/piston valves more suiting to larger calibers.

wyz2285 wrote:Did this a while back


The crooked selector switch in the thumbnail and first scene are bothering me a lot more than they should. :lol:
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Re: Need help with multi shot airsoft gun.

Unread postAuthor: Wallies » Sat Mar 04, 2017 1:33 am

Thanks for the recommendations. The only problem I am finding now is that I can't find any links to hammer valves available online and I would prefer buying one as I have no tools or time to machine a valve myself. Any suggestions?
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Re: Need help with multi shot airsoft gun.

Unread postAuthor: jrrdw » Sat Mar 04, 2017 8:05 am

Wallies wrote:Thanks for the recommendations. The only problem I am finding now is that I can't find any links to hammer valves available online and I would prefer buying one as I have no tools or time to machine a valve myself. Any suggestions?


Get one from a pump BB / pellet rifle.
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When life gives you lemons...throw them back they suck!
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Re: Need help with multi shot airsoft gun.

Unread postAuthor: Wallies » Wed Mar 22, 2017 11:17 am

okay after a while looking at dozens of different hammer valve configurations I have finally decided on a design I saw on youtube. Essentially it is a knock open valve system that works vey similarly to a caselman, but all the part should be able to fit within a 1 inch tube aside from a bolt.
link: https://m.youtube.com/watch?v=TbV3aSoyBIw

Essentially there are two tubes, One being the body and a second that serves a dual purpose of barrel and guide. By running the barrel through the whole body to the valve chamber, It allows the gun to work on an open bolt system. In order to make it full auto capable I decided to seal the head of the hammer with a teflon wafer and I plan on cutting holes further up the barrel, which will allow the escaping air to push the hammer forwards. I also plan on aiding the process by adding a weak spring between the hammer and the valve. which will conserve momentum and allow the gun to cycle easier. To further aid in conserving energy I am using a tension spring instead of a compression spring to decrease the force needed to be applied by the hammer and adding a notch in the bolt while it is depressurized, as the spring would pull the valve open instead of holding it closed.

Any thoughts?
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Re: Need help with multi shot airsoft gun.

Unread postAuthor: jackssmirkingrevenge » Fri Mar 24, 2017 5:08 pm

Any thoughts?


A diagram with what you intend to make would elicit more constructive feedback ;)
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Re: Need help with multi shot airsoft gun.

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