Archive for March 2006
by B.B. Pelletier
Let’s look at something way out there, as far as mainstream airgunning goes. It’s called Convert-A-Pell. According to the research I just did, it’s sold direct off the internet. I’ll tell you everything I know by the end of this posting.
What is Convert-A-Pell?
Airgunners are as curious as cats. They are always thinking of things that relate to airguns, so it’s no surprise that someone thought of powering a pellet with a primer! Actually, this method of propulsion dates back to about 1840, when the first experiments that used percussion caps and very small lead balls were performed. They quickly evolved into a percussion cap that had a ball stuck in it, which was the grandfather of the rimfire cartridge. So this has been done before – many times. Convert-A-Pell is just a modern adaptation of an old process, with an interesting twist.
The “Convert” part is what’s interesting
With the Convert-A-Pell system, you can adapt a firearm to shoot pellets. You get a barrel for a specific model firearm, like a S&W 586, that attaches to the revolver barrel tightly. It does not injure the rifling in any way, because the insert tube is made of brass. You also get six brass “cartridges” that accept lead pellets at one end and a large pistol primer at the other. The advertising says you will get groups of one-inch or less at 15 to 20 feet. It also says a handgun will get about 500 f.p.s.
Airgun Letter tested one with poor results
Back in 1997, Tom Gaylord tested a Convert-A-Pell in a S&W 686 6″ stainless revolver. He had the following remarks:
I tried them in an M1911A1
In 2002 I tried this system in an M1911A1 .45 ACP pistol. I didn’t have the action hang up problem, because the 1911 doesn’t work like a revolver, but all the other problems were there. Accuracy in my test may have been slightly better, say 2″ to 4″ at 15 feet, but it was still nothing to write home about. I didn’t have a chronograph to test velocity.
And, yet, they persist!
What amazes me is that this system is still on the market. After all these years, it should have gone away, which makes me wonder whether Tom or I gave it a good test. I scanned the internet for info, and here’s what I found. For starters, the company seems to have changed hands at least once. The current company seems to have only a website with a phone number, but their last site update was in November 2005. That makes me believe they are still viable. However, they have no prices on their website, and that’s never a good sign.
I tried to find actual test reports on the system but there isn’t much. I did find some mentions on forums that suggest the .22 centerfire system is not too bad. In a single-shot action such as a rolling block, there would be zero functioning problems.
After reading about the product on their website, it looks like the product may have been updated since Tom and I tested it. I mention this because I am not opposed to retesting one, if there is enough interest. By enough interest, I don’t mean one or two persistent people, but a larger crowd.
Is this an airgun? Definitely NOT! Does it have to do with airgunning? Probably, just because it uses pellets. Are we interested? You tell me.
by B.B. Pelletier
Pyramyd Air just sent out a “Spring has Sprung” email promotion that has a special discount coupon attached. The slant of the email seems to be airsoft, but I’ll capitalize on their title and talk about spring air rifles today. A reader who calls himself “twe” says I should address the questions posted to the February 7 blog, HW97 & HW77. Many of those comments asked for comparisons between airguns, probably because that day I broke my rule of NOT comparing one airgun to another. I would now like to explain why I don’t compare airguns.
This is the problem
People say, “I wish you would compare the TF99 with the HW97. And, could you also please list the good and bad points of the Gamo Hunter 1250?” That’s like saying, “Please compare a Corvette to a Toro 5010 riding mower, and could you also list the good and bad points of a shrimp boat powered by a marine Detroit Diesel Series 60? I’m especially interested in the possibilities of interstellar travel using matter/anti-matter propulsion.”
Folks, these comparisons are real hard to do! What do you mean by “good and bad points”? I find the Gamo 1250 too powerful for .177 caliber, but someone else may like it for exactly the same reason. I think the CF-X is very light for an underlever spring rifle, but several of you think it’s quite heavy! Light and heavy, good and bad are all subjective terms for which we will never find complete agreement. So, instead of comparing one spring gun to another, I would like to tell you how the one gun I’m testing performs in several areas I consider important.
What is important in a spring air rifle?
Accuracy, for starters. If you don’t have accuracy there’s no reason to continue. A beautiful air rifle that isn’t accurate is just another inanimate object – a paperweight, if you please. The purpose of an air rifle is to shoot a pellet that hits the intended target. What happens AFTER it hits is in the next tier of comparison criteria, but we don’t waste time on those that miss. There are levels of accuracy that have to be acknowledged or we get stuck real quick. Rather than expound upon them, let me illustrate with a quick little story.
Many years ago, someone had this bright idea: “Ten-meter target rifles are the most accurate air rifles in the world. If I were to increase the power of a 10-meter rifle, it would make a great field target rifle that would dominate the sport.” So they began modifying 10-meter rifles, only to discover that it isn’t easy to raise the power from 5 foot-pounds to 20. Nor is your basic 10-meter gun ready for field target in any other way. Making one over is like modifying a Ferrari to haul manure. It can be done, but what will you have when you finish? And, 10-meter rifles ARE NOT the most accurate air rifles in the world, as it turns out. They are the most accurate 10-meter air rifles. When you try to push them out to 50 meters (for field target), you have to change them so much that they become completely different. They may still be no more accurate than a top-quality sporting rifle that was designed for that purpose to begin with. Before some of you start lecturing me on all the converted 10-meter rifles that are winning field target matches: (1) I am aware of it, and (2) They are no longer ten-meter rifles. And, that’s my point!
Back to springers
Several years ago, I read an article about a guy who poured a lot of money and effort into building what he hoped would be the most powerful spring air rifle in the world. He took the design of a Beeman R1 and made nearly everything larger. The mainspring was HUGE – with the result that the rifle, a breakbarrel, was very hard to cock – about 75 lbs., as I recall. The finished gun weighed almost 12 lbs. What did he get for his efforts? A spring air rifle with about the same power as a Beeman R1! Yes, even when he made everything 25 percent larger, the gun had no more power than a stock R1. So, after accuracy, what’s really important?
That’s MY list. Is yours different? I would hope so. My list comprises the things I think are important, and style comes in very low, while smoothness is quite high. On my list, a Webley Patriot falls below an HW77; and a TX200, which isn’t much to look at, occupies the top rung. It’s the most accurate, it’s ultra-smooth right out of the box, it’s easy to cock for its power and it comes with a great trigger. Is the trigger on a Tau 200 Senior better? Yes, but the TX beats it in all other criteria. Besides, the Tau is a PT boat and the TX is a golf cart. Are you getting my sledgehammer wit?
Before choosing a spring air rifle, consider what you want to do with that rifle. Hunt? Shoot varmints? Plink? Do you want it to be your constant companion or are you looking for something to rest behind the chicken coop door so you can get those rats when they appear?
Specific answers to specific questions
Best springers for field target:
Everything else is like pulling a plow with a Ferarri.
Best springers for a hunter:
All in .22 caliber. Other guns are also useful, but this is MY list of favorites.
Best general-purpose springers:
Notice that power is very low on the list for a general-purpose air rifle.
Best value springer:
Those are my picks. I like all spring airguns, but these have the best combinations of what I look for in a springer.
by B.B. Pelletier
Today is the last post on this topic unless there are questions.
Small bulk tanks
Small bulk tanks have been part of bulk-filling airguns from the beginning. Perhaps the best-known is Crosman’s 10-oz. tank that accompanied their rifles and pistols back in the late ’40s and early ’50s. It was also marketed as a tire inflator to be carried in the car, because those were the days when tires went flat for reasons of their own.
Crosman’s original idea was that shooters would send their empty tanks to a refilling station – BY MAIL! – and wait patiently until their return. Sounds good in the conference room – doesn’t work that way in the real world. That’s where the 20-lb. tanks came into the picture. People were unwilling to wait for their tanks to be returned. Because they’re so simple to fill at home with the right equipment, many of them began doing just that! Pyramyd Air sells bulk CO2 tanks as well as CO2 adapters to connect to certain airguns.
Vintage Crosman 10-oz. tank on bottom; modern 12-oz. bulk tank made from a paintball tank on top. The modern tank has an attached adapter for the Shark pump rifle. Notice the black valve wheel to turn the gas on and off.
Safety burst disks
The Department of Transportation (DOT) requires some kind of positive pressure relief device that can vent certain tanks when the pressure climbs too high. The tanks on which this is required must contain gas at a certain pressure (and higher) and have an outside diameter of two inches or more. The pressure relief device is a small sheet of metal that ruptures at a given pressure. When it bursts, the sound is very alarming, but people nearby are relatively safe. Without it, a tank would explode like a hand grenade. The problem is that not all small tanks have them!
If the tank is less than two inches in outside diameter, it is not required to have a burst disk. Many airguns, such as the Drulov DU-10 and the Tau rifles and pistols, come with these smaller tanks and usually hold 125 grams or 4.4 oz. That’s why I emphasized (in yesterday’s blog) weighing the tank after filling it. Because there is no safety burst disk, you have to make certain there’s enough room remaining in the tank to absorb a great amount of gas expansion. This room has been designed into the tank by the manufacturer. If a small tank is subjected to excessive heat, such as from a fire, it could become very dangerous.
This is the most abused area of bulk-fill operations, because some people will not use their heads! A CO2 bulk tank is rated to a working pressure of 1,800 psi. But, we know that CO2 NEVER gets anywhere near 1,800 psi unless it becomes very hot! So this “working pressure” is really your safety net pressure for when the CO2 tank is heated to 130 degrees F (54.45 degrees C). CO2 at 70 degrees is at 853 psi, give or take. But some people read the number 1,800 and think, “I know everything is really over-engineered. So, if I fill this tank with air to 3,000 psi, that’s not even double its working pressure. It should be safe.” No, you ARE NOT SAFE! You are almost halfway to destruction. If your tank has no burst disk, you will be the last person to know when it blows.
This is how I fill my target pistol. Because the liquid CO2 is heavier than the gas, it collects at the neck of the tank, where it can be pushed into the pistol’s reservoir.
Filling a gun
Every bulk CO2 gun has its own special procedure for filling, so I chose my target pistol – the one I showed you two days ago – as the demonstration gun. To fill this gun, I first remove the protective cap from the threads at the bottom of the pistol grip, then flip the gun upside-down so the grip bottom is pointed straight up. I always put three drops of Pellgunoil into the filling port before attaching the tank. A 125-gram bulk tank is then screwed down tight on the grip. I can hear a brief hiss as the liquid in the tank rushes into the grip reservoir – but I’m not finished. With the tank attached, I cock and dry-fire the gun twice in the upside-down position. CO2 gas puffs out the muzzle heavily when I do this. Then, I wait for one minute before disconnecting the tank. If I follow this procedure, the pistol will have more than 45 shots at good velocity – providing there was sufficient liquid CO2 in the bulk tank to start with. I will shoot only 40 and then refill the gun. In a 60-shot match, I arrange the pellets in my holder so I can see when it’s time to refill.
Connecting the tank, firing two shots and waiting a minute is the entire procedure for filling this gun. Other guns will have different procedures. You have to get to know each gun’s characteristics to fill it properly.
Is this bothersome? Yes, but I have the procedure down so well that nothing can derail me except when my bulk tank runs too low. I miss the positive feedback that manometers give on precharged pistols, but training has taken their place. When I shoot for pleasure instead of competition, I always find a way of counting my shots. Bulk-fill operations require more participation in the process than some shooters may like. However, a good bulk-fill gun can be a wonder to behold. I guess it comes down to making a choice.
by B.B. Pelletier
Today, we’ll learn how to move the CO2 from the large bulk tank to a smaller tank or to the gun, itself.
It takes an adapter
To connect anything to a 20-lb. CO2 tank requires an adapter to connect the big tank to whatever it fills. The threads on the big tank are always the same 1/2″ National Pipe Taper threads (NPT). The threads on the tank or gun you are filling can be anything, including metric, as many of these guns are now coming from outside the U.S. Twenty-five years ago, adapters weren’t much of a problem. The Crosman model 190 gas tank was the most common small tank that needed to be filled, and it has 1/8″ NPT threads. The guns it filled had female threads to match the tank, so bulk-filling was a pretty straightforward process.
Gas comes out on the threaded side. The other side houses a safety burst disk that prevents the tank from becoming a bomb if the internal pressure gets too high.
When the siphon tube was installed, they marked it on the tank so everyone would know in the future – because this tank now operates in the reverse of a tank without the tube.
Outside the U.S., all sorts of other standards prevail, and guns made in other countries use many thread patterns that are not typically found in this country. Your first duty when purchasing a bulk-fill airgun is to ascertain where the adapter will come from to fit that gun or its tank to an American bulk CO2 tank. You have to use an American-approved bulk tank because they are the only tanks for which our DOT has technical data. As a result, they’re the only tanks a filling station may legally fill. This is not a problem, as there are an abundance of bulk tanks, but you always need to think about the adapter situation.
Adapters come in all shapes and sizes. One side fits the large bulk tank and the other fits either a small bulk tank or the gun itself.
The adapter that attaches to the bulk tank has some kind of gas seal on the tank side and perhaps a second seal on the small tank or gun side. These may be o-rings or flat seals, and they have to work because CO2 is under 850 to 900 psi at room temperature. Treat these seals with the same care as your gun seals. They need a light coating of diver’s silicone to maintain their supple sealing ability, and they need to be kept very clean.
Make the connection
Although I used to fill a number of different tanks and guns, I usually shot the same type of gun at any one time, so the adapter for that gun was left on the bulk tank. When making the connection of the tank or gun to be filled, it is important to remember that the adapter seals do the sealing job – NOT the tightness of the connection! Remembering this will preserve the longevity of your adapter seals as long as possible. In twelve years of bulk-filling with nine different adapters, I have never had a single seal fail.
Open the valve!
When you fill from a scuba tank, you open the valve very slowly to keep from overheating the seals from the sudden compression of the air. With bulk CO2, it’s just the opposite. The seals and everything else will cool down during the fill. Therefore, you can make the fill very quickly. I can fill an empty 10-oz. bulk tank in about 20-25 seconds. During this period, the first liquid that enters the empty tank flashes to gas, because the pressure in the empty tank is relatively low. As the liquid changes to gas inside the tank being filled, it cools that tank, lowering the pressure of the CO2 gas inside (remember, CO2 pressure is determined by temperature). Because the bulk tank you are filling from has been sitting in a room for a long time, it has assumed something close to the ambient temperature of that room, so its internal pressure will be higher than the pressure of the gas that’s now inside the tank being filled. As a result, liquid CO2 will continue to flow into the smaller tank. You’ll notice that the outside of the tank being filled will frost up and then melt into a heavy coating of dew. This happens in just a few seconds, and the relative humidity determines the extent of this phenomenon.
Weighing the small tank to be filled
Because there is really no simple way to control how much CO2 enters the small tank during filling, the safe procedure is to weigh the small tank after the fill. Therefore, you MUST know the empty weight of every small CO2 tank you own! By law, a new gun comes to you with an empty gas tank, so that is the time to weigh that tank. Don’t take anyone’s word for how much it weighs until you weigh it on YOUR scale!
This small bulk tank is used to fill my target pistol. The empty tank weighs 1 lb., 6.4 oz., but now it weighs 1 lb., 10.7 oz. There are 3.3 oz. of CO2 inside!
What if you overfill?
An overfill of a small gas tank can be very dangerous, though there is time to deal with it safely if you do not delay. After the fill, the small tank will be very cold, which means the CO2 inside will be at a low pressure. The tank was designed to safely contain a certain amount of CO2 within a certain temperature range. If you discover that the small tank has been overfilled, simply fill your gun from it immediately. (The tank shown in the picture is rated to hold up to 4 oz. of CO2, so it’s not overfilled. Max fill info comes with each new bulk tank.) That drains off the excess gas. You can verify the tank is now safe by weighing it again. If it is still too full, shoot the gun and refill it from the tank. If you don’t have time to do this, simply store the small tank in a freezer until you can get to it again. The object is the keep the tank’s temperature as low as possible until you can get the fill weight down into the recommended range.
Sound too technical?
Bulk-filling CO2 guns is not rocket science. However, you are working with highly compressed gas and there are safety procedures that must be followed. The same is true for filling pneumatic guns from a scuba tank. I have tried to give you as much detail as possible, which I don’t believe you’ll find anywhere else. Even the owner’s manuals of modern bulk CO2 guns don’t go into the detail I have here, but these are things you need to know.
I need one more post to cover all the details I want to pass along, then I’ll wait for your questions to tell me if there is anything else we need to look at. You may be a little confused about how “full” to fill the small tank you’re transferring to. Don’t worry, it’s almost no-brainer. However, I want to spend a little time talking about it, because there are safety considerations.
by B.B. Pelletier
We have discussed bulk-fill CO2 guns several times in this blog. It’s time to talk about how they are filled. Last week, we got a question about this from Jim. Since the answer is not straightforward, I thought it was time to talk about it in some detail.
My 10-meter target pistol runs on bulk CO2 or powerlets. I have set it up for bulk-fill. Gas is stored in the grip.
Meet my 10-meter pistol
My 10-meter pistol is powered by CO2 and can use either 12-gram powerlets of bulk CO2. I have been running it on bulk gas from the beginning – about seven years. I find the bulk method gives me more control over the fill, so I know when it’s time to top off. The importance of knowing the status of a CO2 fill is crucial in a match.
Since few CO2 target pistols have a means of displaying the fill status (how many shots remain), controlling the fill is very important for a competitor. The one time my gun failed me was during an important regional match, when my pistol’s bulk tank was running low and did not give me the fill I had anticipated. I shot a perfectly held 10 that dropped to a 6 (just below the bottom of the bull at 6 o’clock) because of decreasing gas pressure. The four lost points dropped me from the standings in my class (top three places) to fourth place. My type of gun does not have a removable bulk tank like the top-quality target pistols. Instead, my gun is filled in a smaller fixed reservoir by a separate small bulk tank.
Bulk fill as a cost-saver!
Even though my story sounds negative, it illustrates that bulk filling is a method of precisely controlling your CO2 gun. But it’s more than that. It’s also much cheaper. I can bulk-fill a gun for a nickel and get the same number of powerful shots that someone else gets from a 50-cent powerlet. If you shoot gas guns a lot, bulk-filling is the best way to go. Gas-guzzlers, such as the Farco air shotgun (which drinks 2.5 oz. of gas for 20 shots), have to use bulk gas. A CO2 powerlet would only last for one powerful shot with a gun like that.
The red 20-lb. CO2 tank started out as a fire extinguisher. It’s slightly shorter and fatter than the yellow 80 cubic-foot scuba tank to the left.
How do you get set up to bulk-fill?
You need a bulk gas tank. I own three 20-lb. CO2 tanks and one 5-lb. tank that is more portable. The twenty-pounders are similar in size to an 80 cubic-foot scuba tank. They start out life as fire extinguishers and soda fountain gas tanks. They are easy to acquire, though you won’t find them at Wal-Mart. Consult your yellow pages for the nearest industrial gas supplier or restaurant supply house. The industrial gas place will probably also fill the tank for you and do any maintenance you need.
Gas tank requirements
Like scuba tanks, CO2 tanks have to be hydrostatically tested every five years. As a huge user of CO2 10 years ago, I used to consume the contents of a 20-lb. tank in about two years. Calculating the shots I got for a Crosman 111 pistol, one 20-lb. tank provided almost 30,000 shots for $14. That was eight years ago, and the cost of gas has no doubt risen since then. I have purchased two additional tanks in the meantime, both filled, so it’s been that long since I went back to the gas supplier for a refill. A scuba tank holding air may give 2,500 to 3,000 shots per $3 fill in an equivalent air pistol, so both gasses are relatively inexpensive.
A tank needs a siphon tube to draw the liquid CO2 from the bottom.
Bulk tank needs a siphon tube.
Since you want liquid CO2 to come out of the big bulk tank, there has to be a siphon tube inside. It reaches down from the outlet valve to the bottom of the tank. The CO2 gas in the tank pushes down on the liquid, forcing it up the tube and into whatever you connect to the tank. Without the siphon tube, you would have to hold the CO2 bulk tank upside down to force the liquid out first. As heavy as the tank is, you don’t want to do that!
Are large CO2 tanks safe around the house?
Since the other name for CO2 tanks is fire extinguishers, they’re not only safe, they ought to be in every home. Once when some kids abandoned a stolen car in front of my house because the engine was on fire, I put the fire out with one of my bulk tanks. So, yes, they are safe. Just store them where they cannot fall and damage the valves.
Tomorrow, we’ll look at how the CO2 moves from the bulk tank to a smaller tank or the gun, itself.
by B.B. Pelletier
Every bit the Smith & Wesson revolver, this model 586 is a jewel!
I’ve often referred to these revolvers when talking about other models, so today I decided it was high time to give credit where it is due. The S&W 586 and 686 revolvers made by Umarex are the best CO2 revolvers that have ever been made – bar none! They represent the standard by which all other CO2 revolvers are judged. Yet because of their cost, these wonderful airguns are not as popular as the others, which is a real shame. Because it is my opinion that the S&W 586 and 686 revolvers are the absolute top of the Umarex pellet pistol line!
A soft spot for S&W
I have always gravitated toward S&W revolvers. Yes, I had a Colt Python that was as fine as any revolver I’ve ever owned and, yes, I currently own two Ruger .357 DA revolvers that I find very nice. But there has always been something about the S&W action that I liked better than all the others. So when Umarex announced they were coming out with the S&W 586, I was thrilled. I was in tight with the S&W European sales rep at the time the CO2 version of the 586 first came to America, so I got my hands on it about six months before anyone else. Was I ever impressed! The action that is so nice in S&W firearms was almost perfectly translated over to the CO2 revolver. It actually has a better double-action trigger and only a hint of creep in single-action.
Great finish, too!
Surface finish of the early Umarex blued pistols was sometimes flawed by hazy sections that didn’t respond to any treatment. Not all guns had the problem, but enough did that I always examined any new blued gun with a critical eye, and I have yet to see a 586, which is the blued version of the gun, with this problem. The grips are two-piece grippy rubber, very reminiscent of a pair of Hogues – so you don’t have that to buy.
10-shot pellet clips!
The 586 departs from the typical Umarex design in that it has a 10-shot pellet clip instead of the standard Umarex 8-shot clip. This clip is unique to this one model, and the cylinder crane swings out to receive each new clip. The clips are finished only in blue, and I have never understood why Umarex hasn’t made a matching silver clip for the 686! The usually style-conscious Germans appear to either not care about this detail (I don’t believe it), or else the addition of one more SKU for such a low-demand part makes REALLY POOR business sense!
The 10-shot clips swing out to the side on a real crane for removal. Blue (black) is the only color available.
Powerlet hides in the grip
The right grip panel is removed to reveal the powerlet. A lever at the bottom of the grip swings downward to releave tension on the expended powerlet that can then be easily removed. A thumbwheel adjustment compensates for length variation between powerlets. The grip panel is held on by both a clip that grabs the powerlet (so you have to really pull to get the grip off) and some locating features in the grip panel itself. As a result, the grip feels firm and solid when it’s on the gun.
Pop off the right grip panel for access to the powerlet. The lever at the base of the grip frame relaxes tension on the powerlet.
Power and accuracy
Although a revolver usually has a small gap between the cylinder and the rear of the barrel (a few guns have moving cylinders to compensate for this gap) through which gas can escape, the S&W exhibits good power. With the 6″ barrel, I got velocities averaging 410 f.p.s. with Hobbys and 370 with R10s. Though the gun was faster in double-action than single-action, the difference was just 3 f.p.s. with all pellets tested. Usually, a CO2 revolver is faster in the single-action mode, so this is a different airgun, to be sure.
I got group after group of 5 shots measuring less than one inch at 10 meters. That puts the 586 ahead of all other repeating air pistols, save the high-dollar target pistols such as the Drulov DU-10 and the like. Among the Umarex airguns, only the Walther lever-action rifle shoots better.
Is it worth the extra money?
Tough question. A glass of water means a lot to a man in the desert but not to a guy who just fell overboard! To me, it’s worth it. I liked the air pistol so much that I went out and got a 686 .357 to go with it. True story!
by B.B. Pelletier
This one comes from a comment made by Canadian reader Wild Wild West. “Speaking of whisps of CO2, I am not sure if you or any of the other Nightstalker owners have noticed, but on my Nightstalker with a fresh bottle and during the first 100 or so shots, I do get quite an annoying blast of CO2 following each shot.”
Yes, you will see that on many CO2 guns, and today I’d like to examine why.
Liquid or gas?
The way some CO2 guns are designed – whether it’s a full powerlet, removable bulk tank or new AirSource cartridge – it’s possible for liquid CO2 to flow into the gun’s valve when the gun is held level. The liquid CO2 cannot maintain its pressure once it’s released from the confines of the tank, so it flashes to gas wherever it happens to be. If that is inside the valve of a gun or even beyond the valve and inside the gun’s barrel, the CO2 does not have enough time to completely expand before it hits the outside air – still expanding. Because it cools as it expands, it instantly condenses the moisture in the air, creating a fog. The moister the air, the more fog is created.
Vertical vs. horizontal
If you look at AirSource guns, almost all of them align the cartridge horizontally, which means the liquid CO2 inside the full cartridge has the best chance of flowing out when the gun is fired. Now, the AirSource adapter upgrade kit, used to upgrade a standard Crosman 1077, positions the cartridge lower than the rifle’s valve, preventing this from happening. The small amount of vertical space in the adapter allows CO2 gas to rise above the liquid and get to the valve first.
The Crosman NightStalker has the AirSource cartridge aligned horizontally in the butt, so it is a candidate for liquid to flow through the valve. A Benjamin EB 17 pistol has a 12-gram powerlet aligned horizontally with the valve in a tube at the front of the gun, so it is also a candidate for a wisp of fog with the first few shots from a fresh powerlet. On the other hand, a Colt Government Model M1911A1 pistol has the 12-gram powerlet aligned vertically inside the grip, so there is less chance of liquid passing through the valve. A gun like this is a lot less likely to have the wisp of fog from the muzzle on any but the hottest, most humid days.
What about the “dog days”?
There are days when the temperature is so high and the humidity is 100 percent that ANY CO2 gun is going to give a wisp of fog from the muzzle. On days like these, the air is completely saturated with moisture, and anything that changes the conditions for even an instant causes condensation. Just the relative coolness of the CO2 gas is enough to cause visible condensation on a day like this. Heck – even a PCP will smoke on some days for the same reason. I have seen water dripping from the wings of low-flying A10 Warthogs when they turn sharply close to the ground, simply from the air they compress ahead of the wing! They will actually leave brief vapor trails!
WHO – REALLY – CARES?
So what? Now that we know the science behind the smoke from CO2 guns – does it matter? As a matter of fact, it does. If an airgun is passing liquid – instead of gas – through the valve, you can expect the velocity to be way off the norm. If you chronograph the gun, that’s exactly what you’ll find. The first couple of shots from a CO2 gun – ESPECIALLY a gun with a horizontal tank – will be significantly faster than the norm. Then the gun will settle down to a long string of shots in close proximity until all the liquid is gone. Then, the velocity drops sharply.
So a target gun that uses CO2 will have a couple of wild shots before it settles down. That explains why the FWB C55 changed from a horizontal to a vertical gas tank and also why CO2 is not considered competitive at the world level anymore.
“Gee, Mr. Wizard, you sure can tell a lot of neat stuff from just a puff of gas at the muzzle of a gun!”
“Yes, Jimmy, you can.”