Gauged CO2 pellet guns

[Techie]

Why don't we have any gauged CO2 pellet guns?  Specifically I'm talking about a gun with a pressure gauge and method of adjusting the pressure before each shot?  These guns exist for shooting tranquilizer darts or remotely administering medicine to livestock and wildlife.  They work great, eliminating the problem of CO2 producing different velocity at different temperatures.  I use one for darting horses, and I'm shooting .50 caliber 100-grain darts up to 50 yards with it.  Since I adjust the pressure immediately before taking each shot, pressure change at different temperatures is not a problem. 

The amount of pressure I use is based on how far away the target is.  That way I can always hold dead-on, even though these darts have a rainbow trajectory.  You adjust the pressure by bleeding the gas from the main pressure chamber into what I call a "shot pressure chamber", which has the pressure gauge attached to it.  I use standard 12-gram CO2 cartridges, and get about 7 shots out of a cartridge pushing these big heavy darts, depending on how much pressure I bleed off into the shot pressure chamber for each shot.

Here's a link to the rifle I use:
http://www.pneudart.com/products/projectors/gauged-co2/

Previously I used a CO2 dart gun made by Crosman for Pneudart, but because it did not have a gauge, point of impact varied up to a foot at different temperatures.

With the the airgun builders and experimenters we have on this forum, I'd love to see someone customize a CO2 Crosman or SPA Plinkster with a pressure gauge and shot pressure chamber.   In fact, darters would love to see something like a nice light paintball gun adapted for shooting darts.  The Pneudart rifle is $1900 and too heavy, and the lighter weight Dan Inject CO2 dart guns start at $2400 and have to be loaded from the muzzle.

[Rob M]

interesting ., are you sure theyre not regulated,?? co2 can be regulated down to a few psi, the lowest ive seen is 60 psi used on midified nerf dart guns..my guess is theyre not regulated and that you are actually adjusting the transfer port before the shot so animals aren't overpenetrated by the dart potentially causing injury..

[Ribbonstone]

LEts see if this makes you re-think or not.


If I had a Crosman Disco tube with 1 ounce of co2 in it, and another tube with 3 ounces of co2 in it, both at the same temperture, would the pressure gauge read differently?  Would the one with 1 ounce in it read 1/3 as much prtessure as the one with 3 ounces in it?


Yes, do have a couple of HPA QB conversions that also get used with co2 tanks in the summer.  They have pressure gauges on the down side of the bottle (reading output).  So from a full 9 ounce co2 tank to the same tank with 2 ounces of co2 in it, the gauge is pretty much stays the same (if the temperture stays the same)...it pretty much acts as a substitute scale themometer.

[StevenG]

Assuming the tube has enough co2 to liquefy sure it stays the same pressure save for temperature. If it only had such a small amount of co2 that it was a gas the pressure would vary with the fill.

I think he means having a reservoir of liquid co2 and letting a tiny amount of it boil off into a seperate chamber with a gauge.

[Ribbonstone]

OK...a CO2 regulator.   Otherwise, if there is a direct connection (not mechancially pressure controled) then the pressure between co2 tube/tank and valve is going to equalize PDQ (pretty darned quick).


Do remember some trys at a useable co2 regulator in panitball, back in the days befor HPA tanks were popular/available.  Had some problems with up-tipping and direct liquid flow past the regulator, but it might be worth a revisit.

[Techie]

I think he means having a reservoir of liquid co2 and letting a tiny amount of it boil off into a seperate chamber with a gauge.

Yes, this is how I think my dart gun works.  I am the regulator.  Using a knurled ring, I twist that ring to bleed a tiny bit of gas into the shot pressure chamber as I watch the pressure on the gauge rise.  I adjust this pressure to exactly where I want it for that specific shot, based on how far away the target is.  If I end up putting too much pressure on the gauge then I twist the knurled ring in the opposite direction and it bleeds off a little of the gas into the atmosphere, meaning I just wasted a little bit of CO2.  When I pull the trigger, the gas is directed out the barrel and the gauge goes back to zero pressure.  I can repeat this process around 7 times before all the CO2 in the cartridge is used up. 

[Ribbonstone]

A manual lock out/regulation....you control the PSI into the firing chamber and manually lock out any more gas pressure.   


That would work...so long as the co2 in the firing chamber stays the same temp/same pressure after it's locked in place.

[Techie]

That would work...so long as the co2 in the firing chamber stays the same temp/same pressure after it's locked in place.

Exactly.  That's why I don't put any pressure on the gauge until right before I take the shot.  I adjust the pressure based on how far away the horse is anyway.  I know exactly how much pressure I need on the gauge for each range.  Because of the rainbow trajectory of these darts, I need to use a rangefinder and can't be off more than 5 yards, even for hitting a large target like a horse's rump.  These are wild horses, by the way.

[WesBob]

That is very interesting Mike, thanks for sharing, sounds like a project worth trying! Too bad your dart gun is so expensive, a guy wouldn't want to wreck something taking it apart to see how it all works internally.
I converted a 1322 to be a dual purpose dual fuel gun, and gave it to my dad. He had co2 in the auxiliary tank in the fall when it was cool and he was hunting grouse so he would pump it enough times before shooting to bring the pressure up on the gauge. Said it worked good. Made for less pumping than using just air. I realize that is a totally different thing, but is an example of using a gauge anyway to keep velocity stable.

[Wayne52]

I wonder how much this dart gun costs

[Rob M]

I wonder how much this dart gun costs

I like the looks of that gun , bullpup and simple

[Techie]

I wonder how much this dart gun costs

That's a Dan Inject dart gun.  They start at $2395.  I've seen and shot one.  They are smoothbores, and shoot a .50 caliber dart.  I think they are way overpriced for what you get.  It works the same way as the gun I have, by manually bleeding a small amount of CO2 into a one-shot pressure chamber, using a pressure gauge as your guide.  You have to load the dart by sliding it down the barrel, in other words it's a muzzleloader.  If you tip the muzzle down, the dart falls out.  People like them because of the lighter weight.  I'd think any of you airgun smiths could build a better dart gun starting with parts from a 50 caliber paintball gun, and sell it very profitably for less than half the price.  I'm willing to help anyone who wants to try this, at least in an advisor/user/tester/requirements role. 

I tried making my own dart gun using a .50 caliber T/C Contender barrel with a custom breech plug shooting .22 rimfire blanks.  I'm talking about the .22 rimfire power cartridges used to shoot nails into concrete.  They have some dart guns using these.  I found the power cartridges to be inconsistent, and realized you need a smaller flash hole/transfer port because the power and heat from the .22 rimfire blanks would sometimes destroy the base of the dart.  I concluded CO2 or HPA is the way to go with these dart guns, plus you don't have the legal issues of shipping a firearm.  No HPA dart gun exists to my knowledge.   I assume they will eventually come, but you can be the first!  I feel one requirement for success is there should be a quick way to adjust the power right before the shot, as you don't want to hit a close-range animal with excessive force.