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Pneumatic sniper plans

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Pneumatic sniper plans

Unread postAuthor: koolaidman » Mon Feb 04, 2008 6:42 pm

Hey im in the process maybe making a new gun. I had to draw up some skematics to show to my friend and i also rendered it in 3d. Im running this through you guys just for some opinions and trouble shooting.
Im sorry for the link, but i cant resize the pics
http://s259.photobucket.com/albums/hh28 ... render.jpg
http://s259.photobucket.com/albums/hh28 ... m107-1.jpg

simple explanation: the stock is pressurized with a schrader (bike pump) goes to sprinkler piloted with a ball valve (blowguns have crappy flow imo). The breach loading is pretty much a copy of a dude on here who made the "25mm sniper" if i remember correctly, although it wasnt his either. The one difference is that the sleeved inside the 1" barrel will be a 3/4" cpvc barrel to shoot paintballs, tabasco bottles, and 16mm marbles (a little small tho.) The scope is the sweetest part imo, its all pvc and will have plexiglass lenses inside with crosshairs tho no magnification, the cross will have threaded bushings with plugs to screw and seems like it's adjusting, and itll have lense caps on hinges (not shown). The bipod isnt really expressed in the 3d, but there is a diagram on the skematics, basically, theyll fold up. The silencer im still unsure about because of legality so i am open to suggestions.
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Unread postAuthor: niglch » Mon Feb 04, 2008 7:53 pm

That is a very impressive design, I can wait to see it when it's finished. I like your scope idea too. For just being made out of pvc parts it looks pretty realistic. Where are you planning to get the plexiglass for the lenses? I thought about doing something like that a little while ago but I couldn't figure out how I could acquire and cut something that I could use as a lens. Also, how are you planning on making the crosshair?
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Unread postAuthor: koolaidman » Mon Feb 04, 2008 8:17 pm

plexiglass (acrylic) you can pick up at any HD. There is a recommended cutter to use thats only like five bucks, but i just use a jig saw. The crosshair'd just be either like sharpie or thin strips of electrical tape on opposing lenses.
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Unread postAuthor: pizlo » Mon Feb 04, 2008 9:11 pm

VERY nice plans. you have obviously put a lot of thought into this gun and it will defiantly shoot well enough. I do think that a modified husky blowgun valve will serve you better and be more like a trigger. opening a ball with one or 2 fingers will be so slow, that the valve will be piloted before you let out more air than a modified husky will. Your plan should succeeded either way though.
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Unread postAuthor: koolaidman » Mon Feb 04, 2008 9:27 pm

I believed this for a while myself. However, i retested one of my blowgun piloted guns with a ball valve- the power was just about increased 2x. I also believe that a .25" ball valve is quite tiny and easy to flick with one finger when oiled. The way i have it set up is still ergonomical and i think it does still look like a trigger. The only downfall Ill admit though is that you have to reset it afterwards.
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Unread postAuthor: pizlo » Mon Feb 04, 2008 10:00 pm

hmm maybe I'll get a ball and test it out.
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Unread postAuthor: Pyro Ninja » Tue Feb 05, 2008 12:55 am

Only thing I think you should do, is move the schrader valve somewhere else so that it doesn't get foreign objects cloging it up or damaging it.
Anyway fairly good design, Good luck :)
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Unread postAuthor: jackssmirkingrevenge » Tue Feb 05, 2008 1:01 am

I would recommend havign a fixed barrel with an external sleeve for a reloading mechanism, because if you want accuracy then moving the barrel around can't be good.

As to the scope, why not buy a dirt cheap 4x20 scope and hide it in a PVC sleeve?
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Unread postAuthor: koolaidman » Tue Feb 05, 2008 4:42 pm

yeah yeah, i didnt change it on the pics, but i was gonna put the schrader on the side. I was even think of adding another "pod" extending from there just like the gun i modelled it off http://www.firstdefense.com/html/3D50.jpg
Dang that is a wicked cheap scope, the pvc would probly even be just as expensive excluding shipping. It's tempting, however, i think id feel unclean about getting it. For some reason i just like potato guns for the sole idea of turning cheap home depot plumbing fixtures into weapons. Buying an actual scope just wouldnt feel right :| .
Im still thinking about the silencer. Im thinking of just putting on a slip bushing to 1.5" with one or two 1.5" couplers. I guess i just wont add insulation or holes/baffles. Would this somehow be illegal?
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Unread postAuthor: spudy buddy » Tue Feb 05, 2008 7:15 pm

i realy like your design. it's very nice but i would like to ask what program you used to make it 3D and is it free?
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Unread postAuthor: Ragnarok » Tue Feb 05, 2008 7:28 pm

jackssmirkingrevenge wrote:I would recommend havign a fixed barrel with an external sleeve for a reloading mechanism, because if you want accuracy then moving the barrel around can't be good.

Dunno, it works fine on my launcher. I did fit it up so it's got firm supports between the barrel and chamber in three places along it's length though (not really possible on an in-line launcher though), which does hold it down pretty well. Not perfect for accuracy or realism, but it's good for performance - keeps dead volume down, and doesn't have the possible problems that an external sleeve might.

As for the scope suggestion, do it! It can really make a launcher look pretty damn good.
Image

spudy buddy wrote:i realy like your design. it's very nice but i would like to ask what program you used to make it 3D and is it free?

Well, you can easily do that sort of thing in Google Sketchup if you want, and that's free I think.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: koolaidman » Tue Feb 05, 2008 8:39 pm

The program is HASH, not even close to free though. Your better of with another software cause this one is mostly for animation.
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Unread postAuthor: OuchProgramme » Wed Feb 06, 2008 12:01 am

In my opinion, i dont think silencers are good for any pneumatic gun. They dont make THAT much noise. A simple muzzle break is good enough
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 06, 2008 12:08 am

OuchProgramme wrote:They dont make THAT much noise. A simple muzzle break is good enough


Cleary, you haven't dabbled with high pressure or extremely fast and high flow valves. Pneumatics can be *very* loud.

As to the legality of silencers in the US, it's a grey area.

Fair points about the barrel Rag, but it does jar a little with the "sniper" idea, what happened to free-floating :roll: :D
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Unread postAuthor: Ragnarok » Wed Feb 06, 2008 7:46 am

jackssmirkingrevenge wrote:Fair points about the barrel Rag, but it does jar a little with the "sniper" idea, what happened to free-floating?

Well, on the off chance you've got a spudgun that starts shooting notably wide(r) when you get the barrel too warm, and it's barrel is sufficently rigid to manage that, then maybe.

Joking aside, I have been thinking about what can be done to improve spudgun accuracy.
Free floating barrels are hardly a concern when a vast proportion of spudders fire less than perfect ammo from smoothbore barrels, with a often more than a little give in them, I don't think bending from the barrel heating up is a concern.
In our case, rigid, well held barrels are going to be a lot more use than free floating ones.

Take for example HEAL's barrel - even under the 30 bar pressures I'm planning on using, the barrel will expand outwards just 6 microns under that force, and also the barrel won't heat and expand, as it's a pneumatic. That hardly creates a problem that needs a free floating barrel.

But, the barrel has a rigidity of 411.2 Nm<sup>2</sup>, around the same as 1.25" SCH 80 PVC (412.6 Nm<sup>2</sup>). In a barrel with that low a diameter, it's a pretty impressive figure - it's not going to bend that heavily under load.
Under a load of 100 newtons at the end of the barrel, the tip would bend 5.3mm from where it should be - and that would be if it were only firmly held at the very back. Under it's own weight, it would bend just 0.1mm under the same support conditions. (unlike the 1.25" SCH 80 barrel, which actually weighs more and will bend 1.4mm). But as it's tied down in several places, the bend is actually much less.

Under pressurization, these slight bends will create a higher area on the upper surface of the barrel (for the same reason a car needs a differential - the outer wheel will need to travel further in a bend), which will create an upwards force, which will lift the barrel, then it will bend the other way, and it will continue in this manner.
This will turn the barrel into a resonating system, which will throw off accuracy. Less so in the narrower and less initially bent copper barrel than the PVC one, even though it's fractionally less stiff - heck, there are a lot of considerations here, but I'm sure if I go on I'll start killing people off with sheer boredom.

I'll be creating a thread on spudgun accuracy some time, possibly even later today, but I leave you with this thought - as shorter barrels bend less under their own weight, the theory of longer barrels being more accurate isn't necessarily always true.
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