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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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Unread postAuthor: jackssmirkingrevenge » Thu May 12, 2011 12:17 am

cammyd32 wrote:that could be achieved by having a longer push for the bolt so it has to go further until the gas can escape.


Ah, but the bolt cannot be airtight, otherwise it will hang before it is able to reseat. In reality it should be make like this:

Image

You could alter the dynamics and have the bolt blow back instead of forward:

Image
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Unread postAuthor: cammyd32 » Thu May 12, 2011 10:27 am

So essentially is is a pop-off valve, hmm I see your point.
Now I come to mention it I think there might be some possibilities emerging from a blow back design... but there will be quite a few unforeseen problems that will emerge... I will look into it. :D


Update: jsr (and others) this is a new idea I came up with, I saw an idea like this somewhere on this site (a link would be much appreciated) and thought if i could make some kind of a bolt that is blown-back by the air, the same air which fires the bb.
this idea combines the pop-off and blow back bolt designs (where the bb is "pop-ed" off by the charging air. and the bolt is "blown back" by the same air)

[youtube]http://www.youtube.com/watch?v=ty3vONLgyyI[/youtube]

any ideas or thoughts are welcome.
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Unread postAuthor: jackssmirkingrevenge » Mon May 16, 2011 5:08 pm

It looks like it could be made to work, with a spring driven bolt held by a trigger sear. How would you build it in terms of materials? It's fleshing out the design that's usually half the effort.

cammyd32 wrote:I saw an idea like this somewhere on this site (a link would be much appreciated)


this one?

Here's an alternative configuration (can you tell I'm using a laptop with a flipping touch pad...) but really it's getting too complex, this would be easier to make.
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Unread postAuthor: cammyd32 » Tue May 17, 2011 10:36 am

Now (looking at your above picture) we are getting into the realm of paintball guns, *a more simple version of this idea is used in a multitude of tippmann markers (and various other markers) I have even seen air rifles use this firing mechanism http://air-ordnance.com/index.php?osCsid=52d3e8d9ea23cd1869ec57536135712c

I am thinking whether as to actually make a scaled down valve system like the tippmann paintball gun one, as it is a tried and tested valve system. I will then beef it up and make a spring loaded mag for it and attach it to a waist mounted remote tank, so as the tank size will not alter the maneuverability of my gun.
then KABOOM I have a decent gun that I can use for backyard airsoft,...................magic. :D



* = http://www.x7og.net/blowback-internals/12805-comprehensive-front-bolt-powertube-test.html this is a link to a site which has a reasonably detailed explanation of what I mean when I am talking about the paintball gun valve. :) enjoy.
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Unread postAuthor: jackssmirkingrevenge » Tue May 17, 2011 12:48 pm

cammyd32 wrote:Now (looking at your above picture) we are getting into the realm of paintball guns


... meaning things have already gotten too complex. If you're using hard spherical projectiles, you can use a detent and low-flow valve to make a more powerful and less complex launcher.
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Unread postAuthor: cammyd32 » Tue May 17, 2011 2:22 pm

that is a point. hmmm, maybe a new train of thoughts are necessary. perhaps the only way to solve this issue is to put some aggressive looking emoticons;
:violent3: :violent2: :violent1:
ahhh thats much better, 8)

From here I will probably have another look at cartridge designs and hope that some new thoughts unveil themselves. :)
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Unread postAuthor: jackssmirkingrevenge » Wed May 18, 2011 5:49 am

cammyd32 wrote:From here I will probably have another look at cartridge designs and hope that some new thoughts unveil themselves. :)


Self contained cartridges are good because you don't have to worry about a separate gas supply, and a loading mechanism can be easily made analogous to a firearm - bolt action, break action, lever action, straight pull, all these are viable options. With enough power, straight blowback is also an option.

The downside is if you want your launcher to be compact and powerful, you're going to need some very high pressure cartridges with very good valves.

The "valveless" design is therefore a compromise - you need a separate gas supply, but the cartridges are simply sealed tubes with a seal and perforations.

You should therefore first evaluate what you want in terms of the following parameters and build around them:

- performance
- size
- budget
- availability of tools and materials
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Unread postAuthor: cammyd32 » Wed May 18, 2011 12:06 pm

I am thinking that actually bolt action would be by far the easiest method of making any sort of gun, but the amount of cartridges will always be very limited as they cost one hell of a lot more than a single bb and they are hard to mass produce.
I will probably end up making a cheap ghetto prototype out of plastic and pvc (for the gun) but at that the idea will probably phase out and will not continue, thanks to lack of practicality.
hmmm bbmgs are really starting take me in little circles :x , as one idea leads to the next becoming to seem like a good or more practical idea, hmmm (thinks) I tell you what I think there is some credibility in some kind of valveless design but I think I will try and stop focusing on it at the current as I currently have multiple exams. :D
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