pneumatic dart gun

[Forum Admin]

I scrapped the poppet valve, the firing mechanism would be more complex than necessary. I replaced it with a old design using two ball valves, one that blocks the firing chamber from the air reservior, the other one fires the airgun. Using a old CO2 tank as the air storage, it gets 31 shots before it goes from 250 psi down to 150 psi. I plan to build a onboard reservior out of 3/4" type L copper pipe which will lead to the CO2 tank via remote hose. This will make the airgun lighter and have the option of standing alone for fewer shots between pumping if the need should arise. Here's an overall view of the airgun before I add a stock, triggering mechanism, and the onboard reservior:

Here's a closeup of the loading/charging setup:

I'm going to solder a handle on the breech cover to make it look more like a bolt action. The firing chamber is made of a 2.5" length of 1/2" npt brass pipe. The barrel absorbs most of the pressure, so when the airgun is fired, there is practically no noise. I'll try to get some video footage up to demo how it works.

[Forum Admin]

The video is processing as I write this, but I'll post the link:
http://www.youtube.com/watch?v=FmIy5WuZ74U
According to Audacity, it is shooting 300 to 330 fps, putting it around 6 or 7 fpe. This is enough to take rabbits or squirrel with a pellet and more than enough with a sharp broadhead tipped dart. Velocity will improve when the ball valve is opened by a spring. I'll make a few more darts later and do some more shooting over a range of pressures and distances.

[Forum Admin]

Wow! triple post  I tried out some nail darts tonight that weight between 68 and 70 grains. According to audacity, at 225 psi, it is shooting them at 250 fps, or 10 fpe. At 150 psi, it is shooting at 167 fps, or 4 fpe. At 225 psi, it penetrates plywood a tad over 1/2" and at 150 psi, it penetrates a tad over 3/8". This has to be one of the most enjoyable airguns I have ever built. The simple breech loading system combined with the lack of pumping between shots makes it a pure pleasure to use. A proper stock, sights, and trigger, and it will be a deadly small game hunter. Stay tuned for more progress... 

[airgunman]

good one but i cant find metal bottle where to find it and from what is this bottle??

[Pellethuntr]

that's a co2 tank airgunman...IDK if you can by those in your country :/ try online

[Forum Admin]

yep, just a standard paintball co2 cylinder. It is made of aluminum and is very light weight.

[BoyntonStu]

I scrapped the poppet valve, the firing mechanism would be more complex than necessary. I replaced it with a old design using two ball valves, one that blocks the firing chamber from the air reservior, the other one fires the airgun. Using a old CO2 tank as the air storage, it gets 31 shots before it goes from 250 psi down to 150 psi. I plan to build a onboard reservior out of 3/4" type L copper pipe which will lead to the CO2 tank via remote hose. This will make the airgun lighter and have the option of standing alone for fewer shots between pumping if the need should arise. Here's an overall view of the airgun before I add a stock, triggering mechanism, and the onboard reservior:

Here's a closeup of the loading/charging setup:

I'm going to solder a handle on the breech cover to make it look more like a bolt action. The firing chamber is made of a 2.5" length of 1/2" npt brass pipe. The barrel absorbs most of the pressure, so when the airgun is fired, there is practically no noise. I'll try to get some video footage up to demo how it works.

Looking at your breech it seems to me that a smaller opening would allow a dart to load point first and drop into a "v' shaped slot.

My goal would to have the dart sit in the same barrel position as if it were muzzle loaded.

Another idea:  A sliding valve that acts like racking a shotgun to charge the little chamber.

Racking, opens the breech and charges the chamber.

Drop in a dart, close the valve and the breech in one racking motion.

Sure would be neat if it could be done.

BoyntonStu

[FighterAce]

what about a magazine? could you load darts into it with a magazine and just work the bolt like in real guns?
I always wondered if that could be possible...

[Forum Admin]

I originally built the breech for 6" darts, that's why it ended up being so long   Those darts work great in blowguns and have awesome penetration and speed in this gun, but simply arent durable enough to be reused. Nail darts would take a much shorter slot to load into. You could tighten up dead space if the repair coupling was stationary and the barrel slid within it. I chose to have the barrel fixed for greater accuracy. It only makes a 3 to 5 fps difference, so I was willing to make that sacrifice. Adding a couple more psi with the shock pump can make up that difference if I needed it. I chose 250 psi as the fill pressure, since that is the max my modified air compressor can achieve. I'm sick of pumping. lol One of these days I'll find a fridge compressor for higher pressure. Making it pump action to reset the trigger valve and recharge in one racking motion would be awesome, especially if combined with some sort of magazine. All that should be possible, looks like this project will take some time and probably another model to do so. The most I'll probably do to this one is trigger the valve, scope it, and add a stock.
You guys come up with great ideas, I've got a new model brewing already...

***EDIT***
I just added a 24" air chamber under the barrel made of 3/4" type L copper pipe. This allows me to get 10 shots before the pressure drops to 150 psi. 10 standalone shots is pretty nice, with the CO2 cylinder, the number goes to 41 shots.

[airgunman]

hey guys i have one problem!!I made a gun with two valves that can fire several times but when you drop the air and fire
  several times too faint to be given why
  qev I really do not know please help

i will upload video and you will see

[Forum Admin]

I'd like to see the video. Sounds like you need more air capacity. Each time you take a shot, the pressure drops. To compensate, your air reservior needs to be 10x to 20x the volume of the firing reservior. I find that usually gives me 8+ shots before the power drops off too much.

[FighterAce]

This allows me to get 10 shots before the pressure drops to 150 psi. 10 standalone shots is pretty nice, with the CO2 cylinder, the number goes to 41 shots.

wow thats some really high pressure... my maximum pressure is 145 psi lol

[airgunman]

I'd like to see the video. Sounds like you need more air capacity. Each time you take a shot, the pressure drops. To compensate, your air reservior needs to be 10x to 20x the volume of the firing reservior. I find that usually gives me 8+ shots before the power drops off too much.

yes i want to make a video today but air leaks and i must repair that when i repair that i will post a video ! thanks for help i think same that you think i use 1.5 l plasitc bottle

[airgunman]

and btw my new  gun  http://www.youtube.com/watch?v=zpFuJ3Faf0U part 1 and
http://www.youtube.com/watch?v=BYted3C8WDM

[Forum Admin]

Good videos, good luck on getting the leaks fixed. 1.5 L should be enough volume for a good number of shots. Here's a picture of mine ready to be put into a stock:

Here is a picture of the CO2 cylinder that will be used on a remote line and stored in a backpack:

One nice perk about having the onboard air storage is if you leave the charging valve open, you can use heavier ammo and get one very powerful shot out of it. Of course, flow is a bit limited by the 1/4" fittings, but it would be better than the tiny firing chamber.

wow thats some really high pressure... my maximum pressure is 145 psi lol

That is why I like copper so much.  More pressure = more fun. lol