AA-12 Semi-Auto Build

Discussion in 'Gun Building, Modifications & Repairs' started by mikejosephman, Dec 4, 2012.

  1. mikejosephman

    mikejosephman Janice, I'm falling. I'm stuck. This hurts. Staff Member

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    Here's something I'm currently working on. Not full auto, I have some ideas how to do that, but looking to get this done first.

    Body is working out to be around 3 lbs, 1/4 inch sheet metal, two halves that I plan on bolting together at stress points, and also to get at the valve system should it ever need maintenance due to leaking or replacing the valve. The mags will be fused pvc casing, with spring loading almost double stacked, holding about 20 shells. The shells I have been making with 3/4 inch thermal paper inserts. They hold about 23-25 bbs each and have thin plastic sheet glued to the front and back, which easily break through with bbs, but hold up to handling and storage in a standard shell holder.

    I have a few miscellaneous gas valves and tanks, but it just seemed like the simplest method to mount a hookup for a co2 in the stock. Might even make a smaller version that will take 4-5 shells and a 12 gram pod.

    Working on a drum mag here and there. Let me know what you think guys.
    Thanks.
     

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    Last edited: Dec 4, 2012
  2. S0m3_0n3

    S0m3_0n3 New Member

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    I get the feeling you'd need some way to regulate the CO2, otherwise you'd probably have bbs flying at pellet rifle velocities
     

  3. Foshizl

    Foshizl New Member

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    Also an ejection and auto reload system of some sort to get the shells where they need to be for semi-auto purposes.
    Not that I can offer a solution XP.
     
  4. mikejosephman

    mikejosephman Janice, I'm falling. I'm stuck. This hurts. Staff Member

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    Very true and has already been considered, I'm leaving room for a regulator valve to run off a t-section on the left side of the stock close to the grip, that way it can be adjusted on the fly like a hop-up. But pellet rifle velocities I'm not so sure of, I have a 3/4 inch pipe running behind the shell, so exactly the same diameter as the shell, of which only the center 1/2 inch actually has bbs in it. If you've ever seen a plastic receipt paper roll you know what I'm talking about. The holes around the edge of the plastic tube help keep the spread of the bbs tight until well away from the barrel. Without a barrel, the valve shoots pretty soft for unregulated co2, it's not a 1/4 inch opening, know what I mean. I realize this isn't the best for gas effeciency, so that's why I would want to work on a spring powered model.


    Already have that worked out fine sir. The mags I'm constructing are 1 3/4 inches wide. Two shells sitting roughly at 45 degree angle one on top of the other, and spring loaded from the bottom. I have snaked grooves on the front and back of the magazine, little larger diameter than the shells so they can feed upwards into the chamber right behind the barrel opening, and in front of the nozzle.

    The ejection mechanism is nothing more than a metal strip that's housed beside the barrel on the left side, and when pulled back, releases a spring under it, which pushes the shell out of the port. The handle automatically springs forward and flat again on it's own. A shell-catching pouch is definitely making it on my finished version.

    Like I said, "semi-automatic" the shells have to be ejected manually, but they feed on their own. I am hoping to build spring-powered pvc shell version, once I fabricate some molds using this shell, and use a simple piston setup, for lighter weight obviously.
     
    Last edited: Dec 4, 2012
  5. mikejosephman

    mikejosephman Janice, I'm falling. I'm stuck. This hurts. Staff Member

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    The ejection system actually works really well, the handle is off center so as to not be in the path of the sights.
    Was wondering if there is any difference in placing a regulator before or after the air valve, I can experiment and find out I guess.
    Also shortened the barrel to 16 inches, with only 4 inches outside the body of the gun. Could probably use threaded pipe and attach
    a working! silencer, since this has quite a bit of "pop" without one.
     
  6. Courage

    Courage New Member

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    Could we get pics and a video? I know one guy on ASF was making one a long time ago, but it never really turned out.
     
  7. mikejosephman

    mikejosephman Janice, I'm falling. I'm stuck. This hurts. Staff Member

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    Really? Is there any posts or links you could give me to that build? Would be interesting to see some other work.
     
  8. Courage

    Courage New Member

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    Last edited: Dec 4, 2012
  9. mikejosephman

    mikejosephman Janice, I'm falling. I'm stuck. This hurts. Staff Member

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    Interesting. I wouldn't even attempt making an electric blowback version of this gun. If it's not gas(for realism) or spring powered(for use in colder regions) then why bother. Better to sticking to the basic facts that a shotgun uses shells and shoots more than 3-5 rounds per shot. I've been wondering why the cheap spring shotguns only shoot one at a time! For airsoft purposes just makes sense that you would have a shell that holds at least 20, relative to a real shell that holds 20-100+ depending on weight of the grains.

    I just can't understand why it's not already out there, so I'm going to keep working on this.
     
  10. rich635

    rich635 New Member

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    You could use an M210 spring, and use a pneumatic blowback system (like the one's found in G&G) to pull back a heavy slide each shot. Use something like a V7 or even a V2/3, and add 32:1s, a JG Blue, and reinforce and radius that shell to handle the spring. If enough air is used for the blowback, you could have a decently heavy slide at around 300FPS. Not sure how feeding would work though, the air seal would be terrible. Maybe suction cups? I have no clue, just throwing ideas around. Looks interesting though, keep us updated!
     
  11. AirsoftimusPrime

    AirsoftimusPrime New Member

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    For shells try standard springer shotgun shells, they should work fine on semi if the BBs are preloaded into the hopup-type area (l don't know what you'd be using). You really only need to get more complicated if necessary. I know 30rd springer shells can unload in 2/3 of a second.
     
  12. Foshizl

    Foshizl New Member

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    The thing about triple shot shotguns; they have THREE inside barrels that each bb goes through individually. I like his idea on using the shells like traditional shotgun shells: unloading all of it. Plus, it's nice and simple.
    I had thought about recommending triple shot shells to him, but then remember that it may be more complicated than it should be.
     
  13. mikejosephman

    mikejosephman Janice, I'm falling. I'm stuck. This hurts. Staff Member

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    I had considered using current shells, but hollowing the middle out to hold more bbs. Thing is I want this to work the way a shotgun is supposed to, with a spread of bbs, about 10 inch diameter effective at 50 feet mostly. Sure a spring shotgun can act as a sniper rifle of sorts, but just use a sniper then. If pumping out 25 rounds at 250 fps doesn't effect someone within 50 feet, then just increase the FPS via the regulator and make them feel it!

    It's a shotgun, 3 bbs per shot in 3 barrels is just strange to me. Having a larger barrel and using shells that hold more bbs just makes sense. You turn the regulator down for room clearing and close quarters, but still above 200 fps you're sure to make an "impression"!

    Posting a few other ideas in a little while, just got home from work.
     
  14. Courage

    Courage New Member

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    Any pics or vids to show?
     
  15. mikejosephman

    mikejosephman Janice, I'm falling. I'm stuck. This hurts. Staff Member

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    Yeah some crappy pictures with my crappy camera. I will post progress as I can. Thanks for the encouragement!
     
  16. rblevinski

    rblevinski New Member Supporting Member

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    I'm not sure the problem with multiple shots is with the three barrels, or the hop up.

    I am really interested in seeing how this turns out.
     
  17. mikejosephman

    mikejosephman Janice, I'm falling. I'm stuck. This hurts. Staff Member

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    still working out the "kinks" excited!
     
  18. Uller

    Uller Active Member

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    What weight bb's are you considering ussing in this shot gun of yours?It would take a substantial amount of CO2 to propel 20bb's,even .12's,the distance your wanting to achieve.It seems to me 3/4in or even 1/2in is simply to large of a dia to pressurize to make the gun practical.Have you tested any part of the actual firing mech yet?

    My advice to help you along is go to some paintball tech forums,and to make this build alot easier try to refrain from attempting to reinvent the wheel.Do some research into solenoids,and use as much off the shelf components as possible.
     
  19. mikejosephman

    mikejosephman Janice, I'm falling. I'm stuck. This hurts. Staff Member

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    MODS DELETE PLEASE as i'm no longer working on this project at the moment. might return in the future.
     
  20. mikejosephman

    mikejosephman Janice, I'm falling. I'm stuck. This hurts. Staff Member

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    Disregard deletion, have regained interest in this for a summer project. A friend of mine built a CNC machine, now all I need to do is draw up a CAD version of the design, then a few prototype bodies will be cut.