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P. 4 Semiauto bb airsoft gun shooting at 280miles/h

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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Unread postAuthor: thewarp16 » Sat May 17, 2008 3:34 am

yea i have put it almost together but i still need a 15 to 22m reducer will get one soon.

did you make any drewing up of your lever shotty
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Unread postAuthor: Antonio » Sat May 17, 2008 8:01 am

thewarp16 wrote:omg i think i love you i have been looking for a way of firing my lever action shotgun for a long time and i think this mite be the way. after each shot do u need to refill the chamber(coke bottle)

and can u really explain in a simple way how it works im a bit dumb hehe.

thanks man


Hey thnx:) Yeah this thumb reload thing is really really usefull. Plz read the first page of my [urlhttp://www.spudfiles.com/forums/p-4-bb-airsoft-gun-280miles-h-new-with-thumb-reload-t12216.html]postings[/url] as I have all the explanation there. The gun shoots 95 times on a 7 bar 0.5 liter bottle. Plz look at this link: http://www.spudfiles.com/forums/speed-efficiency-test-for-my-p4-airgun-t14330.html It uses a poppet type of valve (homemade) so it can fire 95 times on a bottle. Plz check the first page for explanation, I have lots of animations and vids there.
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Unread postAuthor: nsane-spuds » Sat May 17, 2008 12:01 pm

Wow, 95 shots! thats impressive... I already built multiple hammer valves but the max i could get of an 0.5L bottle was like 25 shots... I know what the problem is but have no idea how to fix it... I usually shoot my gun at around 250 psi which usually shoots the bb at around 500-600 fps. The thing is that at that pressure, I need a pretty big spring to open the valve which causes to much air to come out... I tried different sized springs but its always the same thing... either it shoots 25 shots at 500-600 fps or it just does not shoot because the spring is not powerful enough to open up the valve.
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Unread postAuthor: Tom » Sat May 17, 2008 1:55 pm

nsane-spuds wrote:Wow, 95 shots! thats impressive... I already built multiple hammer valves but the max i could get of an 0.5L bottle was like 25 shots... I know what the problem is but have no idea how to fix it... I usually shoot my gun at around 250 psi which usually shoots the bb at around 500-600 fps. The thing is that at that pressure, I need a pretty big spring to open the valve which causes to much air to come out... I tried different sized springs but its always the same thing... either it shoots 25 shots at 500-600 fps or it just does not shoot because the spring is not powerful enough to open up the valve.


Then it's time to think about changing the piston diameters :D
G's from the Dutch, Tom
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Unread postAuthor: thewarp16 » Sat May 17, 2008 2:40 pm

i just tryed my 22m lever action shotty with the same firing system but it didnt work and its all inside the pipe so i cant see what went wrong.

did yours work the first time u tryed it or did it fail???
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Unread postAuthor: Antonio » Sat May 17, 2008 5:25 pm

thewarp16 wrote:i just tryed my 22m lever action shotty with the same firing system but it didnt work and its all inside the pipe so i cant see what went wrong.

did yours work the first time u tryed it or did it fail???


check this link for more details of the internals I use, eg the valve:
http://www.spudfiles.com/forums/p-3-stacked-tube-t12220.htmlImage
I have been working on airguns for about 5years now:) so yeah things dont come automatically:) One thing is to make things adaptable and acceseble. I you have some pics just post a link here, I wouldnt mind.

nsane-spuds wrote:Wow, 95 shots! thats impressive... I already built multiple hammer valves but the max i could get of an 0.5L bottle was like 25 shots... I know what the problem is but have no idea how to fix it... I usually shoot my gun at around 250 psi which usually shoots the bb at around 500-600 fps. The thing is that at that pressure, I need a pretty big spring to open the valve which causes to much air to come out... I tried different sized springs but its always the same thing... either it shoots 25 shots at 500-600 fps or it just does not shoot because the spring is not powerful enough to open up the valve.

Hey, yeah I know its really impressive. Well ur stuff at 17atm is also pretty cool. Why not try to use a different weight of the hammer. But yeah the higher the pressure the smaller the range. I dont know if you have seen my post on number of shots etc. http://www.spudfiles.com/forums/speed-efficiency-test-for-my-p4-airgun%20-t14330.html the velocity was highest at 6 atm and not at my highest 7.5atm. This shows a similar problem'' as to what you have. Atm I am working on calculations that can give you the best spring constant and hammer mass for the most regular projectile velocity.
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Trigger

Unread postAuthor: littlebro05 » Thu May 22, 2008 3:15 am

Ok i've been trying to figure out how your trigger works from the recent posts, but i was wondering if you held the trigger down when the bb is fired, and continues to hold it down does air come out of the popper valve?

the trigger is probably the hardest thing i've been figuring out, i'm planning to make a similar version of this gun but with the ball bearing as the poppet valve,

i've read the previous posts and it says that each time the shot is fired, the gun "recocks' itself,. so does that mean each time u fire the gun... how does the valve close itself, i've look at the gif images but i still don't get it

could you please help XS
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Don't start crying when I play this as my hobby, Paintball, Airsoft and Nerf are equally good hobbies, except you can play Nerf in public. Good day! Hmph!
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Trigger

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Re: Trigger

Unread postAuthor: Antonio » Tue May 27, 2008 10:04 am

littlebro05 wrote:Ok i've been trying to figure out how your trigger works




Here is the animation of the working. The barrel has a spring over it. When the trigger is pulled the barrel shoots back blockin the load port, then it hits the valve. No its not semi as it doesnt reload byitself. But you can reload it really fast bc of its build magazine and easy handling. I will make some pics of the trigger sometime. If you are building these guns for the first time I would go with a different trigger. I needed lots of experience and time to make this one. I was actually lucky that it worked out as the alligning is really important.

Image

Yes the trigger needs to be held down when you fire. But as the barrel shoot back in less then 1/40 of a second, it doesnt really matter.

Plz look at my other project if you are planning on makin a similar ball valve gun. http://www.spudfiles.com/forums/p-2-very-simple-airgun1-t12712.html Image

If you want to make a really fancy trigger, then look at this one:
http://www.spudfiles.com/forums/p-3-stacked-tube-t12220.html
Image
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Unread postAuthor: littlebro05 » Sat Jun 14, 2008 6:08 pm

ant wrote: Here is the animation of the working. The barrel has a spring over it. When the trigger is pulled the barrel shoots back blockin the load port, then it hits the valve. No its not semi as it doesnt reload byitself. But you can reload it really fast bc of its build magazine and easy handling. I will make some pics of the trigger sometime. If you are building these guns for the first time I would go with a different trigger. I needed lots of experience and time to make this one. I was actually lucky that it worked out as the alligning is really important.


Omg I think i've totally figured out how your gun works... with these steps i think it's how it works

1. The poppet valve spring (p-spring)and the "cocker" spring (c-spring) have about the same about strength. When you cock the c-spring it stores up potential energy and thats where the trigger part jams the barrel.
2. When you pull the trigger the c-spring flicks the barrel back hitting the poppet valve releasing a burst of air.
3. The reason why the poppet valve isn't leaking air is because the c-spring and the p-spring have an almost equal amount of force so both springs are stretched out and air won't leak.

If that's how it works i'm gonna try my gas pistol with your thumb reload.
I'll be so happy if thats how it works and after 3'ish months i've finally figure it out XD
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Don't start crying when I play this as my hobby, Paintball, Airsoft and Nerf are equally good hobbies, except you can play Nerf in public. Good day! Hmph!
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Unread postAuthor: Antonio » Sun Jun 15, 2008 5:15 am

Yeah thats how it kinda works. The factor you forgot though was the pressure that the air exerts on the poppet valve. The higher your pressure the less the valve will open, the lower the pressure the longer the valve will open. So it not static, but dynamic. Thats why its so hard to build autos without using a regulator which keep the opperating pressure at about the same level.
Good luck with ur build:)
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Does it matter

Unread postAuthor: littlebro05 » Sun Jun 15, 2008 5:58 am

Well does it really matter for how long the valve is open for due to the pressure? because when i was looking at your statistics the shots didn't really change much in velocity until it passed like 30'ish psi, from what i can remember... and maybe you should put a hop-up from Kash munni's how to tutorial... it's really simple, and it's probably the thing your looking for to improve the range of your gun XD
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Don't start crying when I play this as my hobby, Paintball, Airsoft and Nerf are equally good hobbies, except you can play Nerf in public. Good day! Hmph!
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Unread postAuthor: Antonio » Sun Jun 15, 2008 7:48 am

Well if the pressure is too high the valve wont open at all. So yeah it is a problem. As you have seen on my speed/efficiency test the velocity drops after 6 bars of pressure. Ofcourse it matters what your spring tension, valve size etc is.
Image

Btw if you have an good ideas just post the links here, I dont mind as it always so hard to find stuff on this forum. So yeah that hopup sounds like a good idea:) as I have tried using it before but never got it to work.
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Unread postAuthor: littlebro05 » Sun Jun 15, 2008 11:47 pm

ant wrote:Well if the pressure is too high the valve wont open at all. So yeah it is a problem. As you have seen on my speed/efficiency test the velocity drops after 6 bars of pressure. Ofcourse it matters what your spring tension, valve size etc is.
Image

Btw if you have an good ideas just post the links here, I dont mind as it always so hard to find stuff on this forum. So yeah that hopup sounds like a good idea:) as I have tried using it before but never got it to work.


http://www.spudfiles.com/forums/how-to-make-a-very-simple-adjustable-hop-up-system-t14776.html

There we go lol. hope that helps you

Edit: Well yeah I just done converting 150km/h-300km/h, but your gun fires at 41.6m/s - 83.3m/s OR for the non metrics about 137fps - 273fps.

Well it looks like you probably paid about $30-$50 making that gun, so it would be as good as a commerical MPEG - Spring Pistol airsoft gun... The statistics are still impressive though
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It's Nerf or Nothing.

Don't start crying when I play this as my hobby, Paintball, Airsoft and Nerf are equally good hobbies, except you can play Nerf in public. Good day! Hmph!
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Unread postAuthor: david » Tue Jun 21, 2011 5:17 am

finally my search for a homemade semi is over! very impressive Ant.

I am curious though. Does the valve spring compress against the elbow joint?

Also, is it only the barrels that slides when the barrel is hammering the valve and returning to position? I think I understand. will have to give it a go. BB guns are illegal without a Gun License here in Australia :(
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