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Descentia · Member

Hi,

I'm a casual airgunner that's looking to get more power out of my Beretta 92FS replica pistol. I was wondering if anyone on these forums knew of a manufacturer that makes compressed nitrogen cartridges to replace 12 gram disposable CO2 cartridges?

Nitrogen has a much faster expansion rate and a much higher release pressure than CO2 stored at the same psi and it appears to be a viable solution to what I'm looking for.

The difference in release pressure should boost my pellet velocity from 450 fps to near 600 fps if not greater, in the event that this could be utilized.

I look forward to your reply,
Thankyou.

AirGunEric · Site Admin

I have not heard of anyone making 12g nitrogen cartridges.

That being said- we may want to consider what you are talking about.

Nitrogen is very similar to air (the air around us is about 90% nitrogen). Carbon dioxide, Nitrogen or air, when compressed significantly, reverts to a liquid state. This liquid must convert back to a gas as the compression pressure is released- which, as you've indicated, can delay things. Not so much really, depending on temperature. The cooler the ambient temperature, the longer the conversion takes- and thus why Co2 guns don't operate as well in cold weather.

That being said- while nitrogen (or air- which would be cheaper) is compressed- it too will become a liquid that must re-convert to a gas for its practical use in airguns. The expansion ratio for nitrogen and air is nearly the same, about 750:1 from liquid-to-gas states, for Co2 it is around 530:1.

So- Nitrogen and air can expand to a larger volume, but the rate of conversion is only faster at lower temperatures. Nitrogen and air are more stable than Co2. The expansion rate of Co2 goes up and up the higher the ambient temperature gets- while Nitrogen and air still remain relatively stable through most of what we would call 'usable' temperatures (let's say 32*F to 100*F).

Now, ignoring this theoretical stuff (I put it in here for future reference)- look back at the expansion ratios of Nitrogen/air to that of carbon dioxide- 750:1 vs. 530:1. What this means in practical terms is that to store the same volume of compressed Nitrogen/Air- a 42% stronger vessel (container) to hold it must be used- i.e. a thicker steel capsule. So- a "12g" Nitrogen capsule (going by physical size) wouldn't hold 12g- but more like 8.5g- so the shot count would be lower per caplet.

Now, throw in that compressed Co2 is used in far more applications than Nitrogen or air (welding shielding gases, restaurant whipped cream dispensers, etc.)- and I don't know if anyone has found a good, financially responsible application for such small caplets. Then throw in that liquid Nitrogen is typically more dangerous than Co2 and the motivation for having "handy" 12g/8.5g caplets of it goes down even further.

It would be interesting to see if someone where to produce air caplets (with the mentioned reduction in capacity to 8.5gr) to use in Co2 airguns or such- but I don't know of any offhand.

You may want to think about "bulking" your gun with a remote tank of compressed air- although you may find the hose/tank situation to be a bit unbearable on a pistol.

Another option may also be helium which has an even higher expansion rate than Nitrogen, air or Co2, and a lower density so the storage vessel doesn't have to be reinforced. But again, that small-capsule format might be the issue. It would be interesting to talk to someone who loads 12g caplets and see if they might be willing to look at helium. Anyone know someone running an industrial gas business that fills 12g caplets for the food industry?

AirGunEric · Site Admin

Oh- and Welcome to AirGunHome.com! Very Happy

Rogerflat · Silver Status Member

I have the same pistol, but I'm wondering why you need the increase in velocity. It's still a piece of garbage bb gun with the worst trigger pull ever. Even at 600 fps you shouldn't be hunting with it, since it is not powerful enough, not to mention inacurate.

Descentia · Member

I'm not sure what problems you were having with the gun, but mine has a very smooth trigger pull and can accuratly shoot 1/8th of an inch at 10 meters. (I'm not steady enough yet to shoot any further).
I personally love the gun.

Back to subject...

I haven't looked into helium at all, but it might be a viable energy source. Although, I've never heard of helium being used as propulsion...

I recognize that an equivalent size N2 cartridge would hold significantly less gas than a CO2 cartridge, I just used the 12g CO2 cartridge notion as an example of size. I'm sure everyone here knows approximately the size of a 12g CO2 cartridge.

I may have found a supplier... http://www.lelandltd.com
Our solution may be found in specification 1.1 and specification 3.1. 1.1 seems to contain our standard 12g airgun cartridge; however, 3.1 has a much higher burst test psi, although a slightly different cap and lower filling density.

ATTN to product numbers:
1.1: 81101, 42101N22700
3.1: 42221, 42222, 42223, 42222N21700

They list the expansion rate per gram of CO2 to be 500cc, N2O 440cc, and N2 800cc. However, the do not list the vapor pressure of N2, but CO2 @ 70 degrees is 850 psi while N2O @ 70 degrees is 940 psi.
Estimating by the expansion rate, it may be safe to assume that N2 at 70 degrees might produce around 1600 psi, almost double that of CO2.
They do not produce helium cartridges of this size.

23ib0d0n · Moderator

Descentia · Member

My gun, as well as, I believe, all 12g CO2 powered guns, has an adjustable plate on which the cartridge sits, so the difference in size wouldn't cause any problem.

I like the solution you showed, but it seems a tad inconvenient.

Even if the cartridge only supplied 1/4 the shots, you would still get 20-30 decent powered shots.

The higher psi version holds 2.8g instead of 3g... I'm not sure which would actually perform better...

DaveK · New Member

You might want to think really hard about the safety aspects.

The CO2 gun is designed to handle pressures in the range of 800 PSI, if I recall correctly. The little N2 cylinders, if you could get them for a reasonable price, are holding gas at up to 3000 psi. Seals, chambers, and other components are likely not designed to handle this kind of abuse. At best, you might get valve lock. At worst, a bunch of tiny pieces flying about at rather high velocities. Somewhere in between is blown seals and permanently deformed parts.

Please! Be careful!

Just my $.02
DaveK

Descentia · Member

Rogerflat · Silver Status Member

Yes, especially when safety becomes an issue then you really want to re-think the reasons as to why you are doing this--among them are ruining the gun, wasting time and money, and perhaps losing an eye.

I think the "theory" behind utilizing different gasses as propellants is fun to pontificate about, however actually going out on your own and rigging this up in order to get a hundred fps more out of a bb pistol is well, pointless.

23ib0d0n · Moderator

I would not be able to fit a cart that is 1/64" longer in either of the co2 guns with the screw on the bottom, and have had to polish some of the co2 carts to wiggle them in and then back out when they were spent.

IF your cart screw has 1/32" more play than a standard cart and IF the cart itself is held to VERY precision tolerences, then please tell us how they work for you Giant Grin

Descentia · Member

I looked further into what DaveK posted and it seems that the tanks used for paintball aren't just directly connected to the guns. The gas has to pass through a regulator which keeps the escaping gas at a set psi.

This taken into account, I think DaveK may be right. The extra psi could permanently damage, if not destroy, the internal workings of the gun.

So, now that we know this, would there be a significant benefit to alternatives such as what 23ib0d0n posted in his picture? In an application like that, you would be able to increase the pressure slightly, assuming that the gun could withstand it. I don't know; however, if nitrogen released at 800 psi would exert more or less force than CO2 released at 800 psi.

Any insight?

Rogerflat · Silver Status Member

What you are talking about now would be like hooking up your PCP airrifle directly to a scuba tank and strapping it on your back and walking around shooting with it. And of course replacing the air with another, more volatile compressed gas. Good luck with it.

p.s. Please videotape your first excursion and be sure to submit the results to youtube

Descentia · Member

No need to be a jerk about it...

Rogerflat · Silver Status Member

Sorry, I thought it was kind of funny--what with seeing someone so dead set in blowing themselves up and all.