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I (sort of) has full auto :D

Built a BB Machine Gun? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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I (sort of) has full auto :D

Unread postAuthor: jackssmirkingrevenge » Sun Jan 11, 2009 12:14 pm

Following on from this experimentation, I cobbled together a functioning setup just to at least prove that the concept is workable. It's all very ghetto and would need a bit of fine tuning to be reliable, but as you can see from the last video, the power potential at the 110 or so psi I'm limited to makes it just not worthwhile. I did develop a fondness for pop-offs however so there is a little idea that I might be revisiting :) In the meantime, enjoy some videos and a pic of the dismantled unit.


[youtube]http://www.youtube.com/watch?v=X5cQHU66PgE[/youtube]


[youtube]http://www.youtube.com/watch?v=yRbXIlmc4Ng[/youtube]


[youtube]http://www.youtube.com/watch?v=OooDC02HPKc[/youtube]


[youtube]http://www.youtube.com/watch?v=RTqItJA1wOs[/youtube]
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Unread postAuthor: ALIHISGREAT » Sun Jan 11, 2009 12:24 pm

I like the sound, its almost like a sci-fi ray/lazor gun.
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 11, 2009 12:25 pm

ALIHISGREAT wrote:I like the sound, its almost like a sci-fi ray/lazor gun.


That's my cellphone camera, it tends to make everything sound like that.
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Unread postAuthor: Sticky_Tape » Sun Jan 11, 2009 12:49 pm

Chook chook chook chook I like it it has a really high rof or alot of double feeds :P I think you should make a a barrel sealing valve chamber fill with a spring behind the piston and a pop-off pilot. That should slow down the rof and give more power.
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Unread postAuthor: dudeman508 » Sun Jan 11, 2009 12:51 pm

So tell me if im wrong its like a mini piston with the pop of as the pilot valve?

ps i saw you online playing call of duty at my friends house last night
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 11, 2009 1:08 pm

Sticky_Tape wrote:Chook chook chook chook I like it it has a really high rof or alot of double feeds :P


As I said, it would need some work to feed and cycle reliably, however this was made purely for the sake of putting a few rounds through the mechanism as it seemed a shame not to.

I think you should make a a barrel sealing valve chamber fill with a spring behind the piston and a pop-off pilot. That should slow down the rof and give more power


That's basically the plan, though I think I would rather use it in conjunction with a cartridge feed than blow-forward bolt.


dudeman508 wrote:So tell me if im wrong its like a mini piston with the pop of as the pilot valve?


You are in fact wrong, there's no mini piston - the pop-off valve is the firing valve, and exhausts into the breech.

ps i saw you online playing call of duty at my friends house last night


Must have been someone else ;)
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Unread postAuthor: psycix » Sun Jan 11, 2009 5:52 pm

And yet again you compensated your fail.
Win on the lazor soundz! :D


So this is a blow-forward bolt together with a pop-off?
At what pressure does this popoff open, and on what pressure does it close?
(most popoffs close at a different pressure then they open, which allows you to do stuff like this)

You just put full flow trough the blowgun, or is there a restriction built in?


Good work! Keep on tweaking and maybe try to fix that double feed.
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Unread postAuthor: Davidvaini » Sun Jan 11, 2009 6:47 pm

one thing I would suggest is adding a spring in the magazine... this way you dont get bb's popping up and you might reduce your misfeeds.
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Unread postAuthor: Lentamentalisk » Sun Jan 11, 2009 8:58 pm

dudeman508 wrote:ps i saw you online playing call of duty at my friends house last night


Jacks Smirking Revenge is not something he made up, it is a Fight Club reference. It is an awesome name, so others have probably taken it up.
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Unread postAuthor: inonickname » Sun Jan 11, 2009 9:04 pm

That's awesome :o I likey. (cool deathray!)
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Unread postAuthor: POLAND_SPUD » Sun Jan 11, 2009 11:06 pm

well it seems it works ok

tweaking will take some time... that's for sure

Do you plan to use higher pressures ?
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Unread postAuthor: jackssmirkingrevenge » Mon Jan 12, 2009 12:12 am

psycix wrote:So this is a blow-forward bolt together with a pop-off?


That's it, I used the variation suggested by ilovetoblowthingsup for smoother operation

At what pressure does this popoff open, and on what pressure does it close?


It depends on how you tweak it, as it is the setup doesn't work below 75 psi.

You just put full flow trough the blowgun, or is there a restriction built in?


There has to be a restriction, otherwise the pop-off will stay open. The setup needs to be like this:

air supply -> restriction -> firing chamber -> pop-off valve

This way, when the firing chamber reaches firing pressure, the pop-off dumps pressure then closes, allowing the firing chamber to fill up again, getting up to pressure and so the cycle repeats. You can change rate of fire by varying this restriction, less restriction means greater rate of fire. Removing the restriction gives you a rate of fire of "infinity", so to speak, as the the valve will stay open as long as there is air supply.

In this case, the "firing chamber" is the hose between the blowgun and the compressor, while the restriction is the compressor's tap.

Good work! Keep on tweaking and maybe try to fix that double feed


I don't plan on developing this any further, the idea now is to build a pop-off actuated piston valve and combine it with a cartridge feed system (or just direct blowback if I'm feeling lazy :roll: ) - still, anyone who wants a low powered full auto airsoft MG has a basis for some development with this design, which has lots of room for improvement like:

one thing I would suggest is adding a spring in the magazine... this way you dont get bb's popping up and you might reduce your misfeeds.


:D

Do you plan to use higher pressures?


If I had an HPA setup I would be inclined to try, but my SCUBA tank is a hassle to fill so I'd rather keep it for filling my PCPs. What I'm going to go for is a more powerful valve that will hopefully give decent power in the 80-110 psi range.
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Unread postAuthor: inonickname » Mon Jan 12, 2009 12:22 am

I know your wanting to change it, but this is just a suggestion: if you're using bb's (metal) glue a small magnet underneath the barrel below the magazine. As long as it isn't too strong, it'll hold the bb until firing.
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Unread postAuthor: jackssmirkingrevenge » Mon Jan 12, 2009 12:30 am

inonickname wrote:if you're using bb's (metal) glue a small magnet underneath the barrel below the magazine


Not a new idea, but in my case the ultimate goal is to use lead pellets as ammunition, to move away from the "BB hose" BBMG concept.

Adapting this design to 0.177" BBs would probably give better performance though, a spring loaded tee magazine like the one below would be easy to make. Actually, I just might make one to give it a go.

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Unread postAuthor: inonickname » Mon Jan 12, 2009 2:02 am

jackssmirkingrevenge wrote:
inonickname wrote:if you're using bb's (metal) glue a small magnet underneath the barrel below the magazine


Not a new idea, but in my case the ultimate goal is to use lead pellets as ammunition, to move away from the "BB hose" BBMG concept.

Adapting this design to 0.177" BBs would probably give better performance though, a spring loaded tee magazine like the one below would be easy to make. Actually, I just might make one to give it a go.

Image


Aww, hadn't seen that before but I guess nothing is new on the internet.. always someone who did it first. Not sure what you can get over there, but here you can get rectangular brass tubing in various sizes from hobby shops. It's with the other pipe etc. I'm sure you could get that to work.
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