Topic: Homemade Semi-Auto Idea. Plausible Or No?

Building or modifying BB, Airsoft, and Pellet type of guns. Show off your custom designs, find tips and other discussion. Target practice only!
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Vudu
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Mon Mar 23, 2009 4:30 pm

Here are my design pictures for a gun that I intend to build if it seems it would work.


First Up Is The Externals.
Image

Next Is Internals.
Image

Then All Together In One Mockup.
Image

My pictures were done in GIMP 2.0, and are not exactly scaled properly, but it still gives you a general view of the plans.

Just so you know, I am not noob to the whole forum business, and I do realise that idea threads are generally frowned upon, so I will ignore all flames regarding posting an idea topic. I fully intend to make this, IF the idea seems to be plausible.

So; Questions, Comments, Flames?

- Vudu
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jackssmirkingrevenge
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Mon Mar 23, 2009 4:38 pm

We don't ideas as long as they're well presented :)

A few more details would be welcome though, what calibre is it, what's the propellant gas and at what pressure, what's your valve? The diagrams aren't very clear.
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POLAND_SPUD
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Mon Mar 23, 2009 4:55 pm

for me it looks like an air-ram design (.....waiting for rag to start arguing :wink: ) without a QEV

nahh sorry it seems that he wants to use something similar to a spool valve.. the spool is actuated via a rod connected to the trigger
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jackssmirkingrevenge
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Mon Mar 23, 2009 4:59 pm

I think much thought has been given to the aesthetics and not much to the actual mechanism, best get your priorities right - better an ugly launcher that fires than a pretty one which doesn't ;)
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Vudu
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Mon Mar 23, 2009 5:01 pm

Mmk, well, The ammo I will be using is .25's, the propellant gas will be provided from either a bike pump, or a compressor, the pressure I do not know yet, but I can get a bike pump that goes up to 150 psi. How much pressure would I need for 300-400 fps? The valve is a simple two step. I will explain how the gun works further. Also, would I need a regulator?

So, to get this gun shooting (In Theory), you fill the tank on the bottom right through the tire valve on the bottom, using either a bike pump, or compressor. The air goes through the tank, into the right hole of the valve, which fills the pressure chamber. When you pull the trigger, it pulls forward a piece of PVC, which is slid over the PVC mock barrel, in turn pulling forward the firing pin. The pressure chamber moves forwards, using the second piece of the bolt to stop the air flow from the tank. The pressure chamber opens to the hole to the barrel and releases it pressure. Upon release of the trigger the entire firing mechanism reverses, refilling the pressure chamber, and preparing for the next shot. It would also not be too difficult to add in a breech, and the regulator would do it's duty and make sure all my shots are consistent.

Also, has a high capacity clip ever been made before? As in, one which you wind up?
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Vudu
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Mon Mar 23, 2009 5:03 pm

jackssmirkingrevenge wrote:I think much thought has been given to the aesthetics and not much to the actual mechanism, best get your priorities right - better an ugly launcher that fires than a pretty one which doesn't ;)
Nah, it's just a simple mechanism. The looks are just a shell.
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Ragnarok
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Mon Mar 23, 2009 5:36 pm

Looks somewhat like a cross between the Pancor Jackhammer shotgun and the TDI Vector submachinegun, both of which are firearms of an interesting appearance, so no complaints on that front.

However, as for what pressure is needed for a given velocity, it does have a dependence on barrel length and valve, and to a lesser extent, specific chamber size.

We can say "ooh pretty appearance", but our primary expertise here is the functionality of these things, and to give feedback on that we do need more numbers and preferably reasonably detailed diagrams.
It's hard to work just from a paragraph of description.
Also, has a high capacity clip ever been made before? As in, one which you wind up?
Before someone less forgiving slates you for it, there is a difference between clips and magazines, and the terms are not interchangeable.

Clips are bits of springy metal that hold a round by the rim on it's base for feeding into a magazine. Magazines are those systems which take a direct part in feeding a round* into the breech, usually by a spring mechanism - they may be either integral to the gun, or removable and interchangeable.

9 (or more) times out of ten, when someone says clip with reference to a firearm, they really mean magazine.

*Arguably, round is similar term. Round only technically refers to the combined bullet, case, powder charge and primer together - it's common to see it used to refer to the projectile.
Does that thing kinda look like a big cat to you?
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Vudu
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Mon Mar 23, 2009 5:49 pm

Hmm, I knew something was up when I said clip. :roll: Just didn't recognize it I suppose.

Back on topic, I will write up the sizes and materials I intend to use for this weapon, and I could make a more in-depth view of the valve if you would like.

But would I need a regulator or no? From what I understand I would need one, but possibly not?

To those of you into Nerf, the pressure chamber will hold just slightly less than an AT2k chamber. Would this be too much or not enough?
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Mon Mar 23, 2009 5:58 pm

Wow, nerf pressures are a bit, say, 'weaksauce' around here. You'd do good to crank that mother up as far as you can get it.
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Vudu
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Mon Mar 23, 2009 6:30 pm

I was talking in relevance to air mass rather than pressure. :) Sorry, shoulda cleared that one up.
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Tue Mar 24, 2009 1:10 am

Download Gas Gun Design Tool, it's a brilliant application that allows you to virtually model your launcher in terms of performance and you can tweak the parameters such as chamber size, pressure, barrel length etc. until you get optimum performance ;)
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Vudu
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Tue Mar 24, 2009 7:48 am

Oooh. Sounds like a fun thing to do. Thanks. :)

Edit>> So I downloaded it, but it didn't work right or something. It just won't open, claiming something is missing or corrupt.
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Ragnarok
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Tue Mar 24, 2009 6:03 pm

Vudu wrote:So I downloaded it, but it didn't work right or something. It just won't open, claiming something is missing or corrupt.
Did you download the full package, or just the executable?

Also, you'll have to download version 4.6 - the earlier versions are dead links.
Does that thing kinda look like a big cat to you?
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Vudu
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Tue Mar 24, 2009 7:42 pm

At first I downloaded just the executable, but now I downloaded the full package and it still won't work.

Edit>> Got it working. Can't believe I hadn't checked this earlier, but apparently this whole Vista thing sucks bum. Basically I just had to run as an administrator. :oops:
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Ragnarok
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Tue Mar 24, 2009 8:07 pm

Vudu wrote:Got it working. Can't believe I hadn't checked this earlier, but apparently this whole Vista thing sucks bum. Basically I just had to run as an administrator. :oops:
Oddly, there seems to be a some method for deactivating that, because I'm running Vista and don't have to bother with permission boxes, etc.

The problem is, I'm not quite sure how I managed it.
I think it it may have been activating Admin privilege on the properties, running it, then deactivating the control again.

Whether it's then running at Admin level without having to ask every time or running without Admin privilege (as D_Hall, it's creator says, it shouldn't need it), it's not asking each time.
Does that thing kinda look like a big cat to you?
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