All about AirGuns


As I am just starting to collect air guns I don’t have much of a collection yet. But so far II own two types of pistols, a CO2 BB pistol and a Spring piston pellet gun.

The most common types of airgun pistols today are:

CO2, Single-stroke pneumatic, Precharged pneumatic, Multi-pump pneumatic, Gas spring air and Spring Piston.

Some examples of Spring Piston pellet are:

 

Browning 800 Express @ $149.99

Browning Buck Mark Air Pistol @ $44.95

IZH 53M Air pistol @ $79.95

Diana RWS LP8 @ $259.95

Beeman P1 Air Pistol @ $459.95

Hatsan Model 25 Supercharger Air Pistol @ $129.99

Ruger Mark 1 Air Pistol @ $64.95

Beeman HW70A @ $279.95

Beeman P5 air pistol @ $199.99

Beeman P11 air pistol @ $519.95

Cometa Indian Air Pistol, Nickel @ $218.50

 

Why you DON’T want to break the sound barrier

August 23, 2011 

This report has been done in bits and pieces many times over the years, but I’m putting it together today because of a surge of new airgunners coming online. Many of them are older firearm shooters, but many others are younger shooters with no real background in the shooting sports. We’re seeing an upturn of fundamental questions in our social networks and through customer service representatives that tell us that this topic needs to be emphasized once again.

What’s wrong with the sound barrier?
The sound barrier is a lot more familiar to people of my generation, because it was being talked about and always in the news when I was a youngster in the 1950s. Young folks don’t think much about it these days because supersonic flight is a foregone conclusion; but back in the 1940s, it hadn’t yet been achieved by a manned aircraft in level flight. A couple pilots inadvertently broke the barrier in dives from high altitude during World War II when they were testing certain fighter aircraft, and one of them was Cass S. Hough, the grandson of the founder of Daisy and later a president of the firm himself. At the time, he was trying to solve a control surface problem with the twin-engined P38 Lightning fighter, so he took one to over 40,000 feet, nosed it over into a steep dive and might have become the first man to ever break the barrier in an airplane. I say “might” because almost every air force of that period has a similar story. There’s a plaque in England that commemorates that flight in 1943, but I’m sure there must be other plaques in other countries, as well.

Before I hear from all the engineers (except the aeronautical engineers) that a prop-driven plane cannot go supersonic because the propeller has to break the sound barrier long before the aircraft does, it is possible — when gravity assists the aircraft — for a prop-driven plane to go supersonic. It’s not a good thing. As Hough discovered, the subsonic control surfaces no longer work right at supersonic speeds, but it can be done. As a result of Hough’s flight, the P38 received a special “dive flap” control to help free the controls when the speed got too high.

The problem with the sound barrier is what happens as you approach it and then pass through. In short, a pressure wave of air builds in front of whatever is moving that fast. Normally, this pressure would then flow around the surfaces of the aircraft and be left behind — but at transonic speed, the air compresses and develops eddies and currents that play havoc with the control surfaces of the aircraft. The surfaces that work well up to a certain subsonic speed start to act odd when they reach the transonic speed, which is about Mach 0.9, or nine-tenths of the speed of sound in the conditions of the moment.

One bad effect of reaching the sound barrier is a buffeting that causes the entire aircraft (or pellet) to vibrate. Aeronautical engineers had to learn to design aircraft for supersonic flight while maintaining the ability to fly at subsonic speeds as well.

Now, let’s talk about pellets
Pellets don’t have adjustable control surfaces. They are what they are, so they like to fly at certain speeds, and in all cases with standard diabolo pellets (wasp-waisted with a hollow tail) that speed is subsonic. In fact, even the transonic region is bad since it’s the place where the buffeting starts.

Why we don’t want 1,000 f.p.s.
This is why we do not want to shoot pellets at 1,000 f.p.s. Because 1,000 f.p.s. is always in the transonic region.

How fast is the sound barrier?
The answer is: it depends. Things that change the speed of sound are the elevation above sea level, the ambient temperature and humidity. Elevation is subtle, because it also influences the air temperature. Temperature of the air is the most influential factor that affects the speed of sound, and I’ve learned that where I live the barrier can exist anywhere from about 1,060 f.p.s. and above. The usual speed of sound is given as about 1,125 f.p.s. when all conditions are “normal.”

You know the pellet has exceeded the sound barrier when you hear a sustained crack with the shot that cannot be attributed to the muzzle blast. Silenced firearms dramatically show off this sustained crack because the bullet is quiet at the muzzle and then returns an indistinct sound like distant thunder as it goes downrange.

But, it isn’t the sound that airgunners should be concerned with. It’s the accuracy, or rather the lack of it that is caused by the buffeting mentioned earlier.

How pellets are stabilized
Pellets are stabilized both by spin and drag. Since they are hollow, they are light for their length, so the spin can be slower than for solid conical bullets. That’s why solid pellets are usually a failure.

But pellets are also stabilized by high drag, just like darts. The wide hollow skirt creates a low-pressure area behind the pellet that drags on them as they fly forward. It keeps the point oriented forward and stabilizes the projectile in flight.

At subsonic velocities, pellets are usually stabilized pretty well; when they get up into the transonic region, they’ll flutter in flight, just like those older airplanes did. And, those flutters translate into larger groups. Knowledgeable airgunners like to keep their velocities under 900 f.p.s. for safety’s sake.

One additional reason to stay below the transonic region
I was chatting with Mac about this; and we’ve both observed that in spring guns, the faster they shoot the twitchier they are as far as hold sensitivity. That has nothing to do with the sound barrier — it’s just a fact of life for spring guns. Throw in the breakbarrel design that’s also very hold sensitive and you have a real recipe for disaster. Yet when you look at all the magnum airguns that are being sold on the basis of velocity, the majority of them are breakbarrels.

So, we have a bad situation in which the most inexperienced shooters are drawn to the very airguns that are the most difficult to shoot on the basis of two things — the advertised velocity and the low cost! It’s like a church that decides to hold its meetings in the piano bar of a casino.

I’m on what, I guess, is a lifelong crusade to spread the word about airgunning so people don’t come in the wrong doors and find things amiss. I want to give each new shooter the same chance I had to discover the shooting sports on the very best terms. If they could just see a fraction of what I see, I know that many of them would be intrigued enough to stay and grow our hobby.

Airgunning can be fun and very satisfying if you do it the right way. The right way is to shoot enjoyable guns that hit their targets more often than not. Hyper-velocity airguns are the antithesis of that. They are the .338 Lapua Magnums whose owners have each fired one box of ammo before giving up on the beast.

 

 This report is for all the new airgunners who have asked for descriptions of airgun powerplants. The ones listed here are found in traditional airguns, which means pellet-firing and steel BB-firing guns. This is not a look at airsoft powerplants, though some of those are virtually the same as some of the ones described here. Don't confuse this site with Airsoft equipment. This is all about true bb and pellet guns.The difference between Air Guns and AirSoft guns? Airsoft guns fire plastic bb's or pellets versus lead or steel shot for my Air Guns. The velocity and  

Pneumatics
A pneumatic gun uses a stored charge of compressed air to propel a projectile. Because the pneumatic powerplant has so little moving mass and because it's less sensitive to temperature than any other airgun powerplant, it's the easiest type of powerplant to shoot accurately. The field of pneumatics is further broken down into four principal categories.

PCP
The Evanix Blizzard S-10 is a good example of a modern PCP.

Precharged pneumatic (PCP): This is possibly the oldest type of airgun powerplant--dating to some time before the year 1600. PCPs store an air charge in a reservoir, then release part or all of it when the gun is fired. Most big bore airguns are PCPs, as are most target guns and precision sporting rifles. In Europe and among target shooters everywhere, this powerplant is called compressed air.

multi-pump
Benjamin 397 and 392 are classic multi-pump pneumatics that have been around for over 50 years.

Multi-pump pneumatic: Multi-pumps date back to at least the 18th century but were reborn in America at the start of the 20th century. Today, they're found chiefly on low-priced sporting guns made in America. They require multiple pumps of a built-in lever to compress an air charge for firing--typically from three to eight or even ten.

Almost all multi-pumps are single-shots, but in the past some were made as repeaters. Repeaters take from 20 to as many as 250 pump strokes to charge completely, but you then get 10, 20 or even more shots without recharging.

single-stroke
The HW 75 pistol is a single-stroke pneumatic. Made by the Weihrauch factory in Germany, it's easy to cock and quite accurate.

Single-stroke pneumatic: Perfected in the 1960s, single-strokes are just what they sound like--guns that use a single pump stroke to pressurize the firing charge. If you attempt a second stroke, the air from the first stroke will be released. This powerplant is primarily found on target guns and low-priced guns geared toward the youth market, though there was a semi-successful single-stroke sporting rifle made in England several years ago.

CO2
Looks, shoots and handles like a firearm. The Walther CP88 is a firearm lookalike. It uses one 12-gram CO2 cartridge, which fits in the grip.

CO2
Yes, it has occurred to many people that carbon dioxide (CO2) is not air at all. Still, you will always find the CO2 guns included with airguns. Carbon dioxide is a refrigerant gas that expands dramatically at room temperature. At 70 deg. F, it produces 853 psi (pounds per square inch) of pressure. If introduced into a gun as a liquid, CO2 provides steady power for many shots. Because it's a refrigerant, CO2 will cool the parts of a gun as it passes through at firing. As the gas becomes colder, the pressure drops and, below 50 deg. F, CO2 is not very efficient.

CO2 was first used in the middle 1800s, but Benjamin and Crosman both pioneered its use in the 20th century. Liquid CO2 is put into convenient Powerlets (a term coined by Crosman, the company that invented the 12-gram size used in airguns) for ease of handling. It can also be put into guns from large bulk tanks. Normally, CO2 provides the lowest power potential of all the airgun powerplants, unless something drastic is done. The most practical way to get higher power from CO2 is to use a heavier projectile and a longer barrel.

Spring-piston guns
Spring guns appear to be an invention from the 19th century, though one type of spring gun--the bellows gun--dates from at least a century earlier. They're simpler in construction than the gas guns, with fewer moving parts, but they also have less potential for power than pneumatics and even CO2. Still, shooters like them for their simplicity. Today's typical spring gun falls into one of three categories.

spring-piston
The Gamo Whisper is a breakbarrel spring gun. Other cocking methods for spring guns include sidelever and underlever actions. The Whisper is one of many guns whose coiled metal springs can be replaced by a gas spring.

Coiled steel spring: This is by far the overwhelming leader in spring guns. A coiled steel spring drives a piston forward to compress air in a compression chamber. At the far end of the chamber, a hole called a transfer port lets the compressed air escape and get behind the projectile in the barrel. The steel spring technology has changed from a coiled volute spring in the mid-1800s to a coiled wire spring today.

Gas spring: Argentine airgun designers were apparently the first to adapt gas springs to airguns, but Theoben of England made them famous. They're also called gas rams and gas struts. Gas springs are longer-lived than coiled steel springs, plus they can be rebuilt. They act faster than coiled steel springs and have less mass, which lowers both the recoil and vibration of the gun. On the outside, gas spring guns look exactly like guns with steel springs.

catapult
Did you own a Red Ryder BB gun as a kid? It's also considered a spring gun.

BB guns (Daisy-type mechanism): The BB gun mechanism is a hybrid of spring-piston design. It also uses catapult technology (explained below) to enhance the effect of the compressed air charge. Not all BB guns use this special type of powerplant, but the Daisy Red Ryder is the poster child of those that do.

sharpshooter
The Sharpshooter is one of many catapult guns that use mechanical force rather than compressed gas to launch a projectile. This brand traces its roots back to 1923, though this particular model was probably made in the early 1980s. It shoots a single No. 6 lead shot, which is nominally 0.118" in diameter. The gun is safe enough that it won't break a window, yet with rubber bands it'll kill a fly at 10 paces. These guns are remarkably accurate at short range. And, they're repeaters!

Catapult guns
Like CO2 guns, the catapult gun is not an airgun, strictly speaking. Still, you'll usually find it positioned among airguns because of its low power and quiet operation. Instead of an air or gas charge propelling the projectile, a mechanical catapult launches it.


Catapult guns have existed since at least the late 1500s in the form of the stonebow. In the 1840s, Hodges in England built a catapult gun larger than .40 caliber. Spear guns that use elastic bands are also catapults.

The best-known airgun example must be the Sharpshooter pistol that was invented by a dentist in 1923. Daisy once marketed a catapult that looked like a single-action revolver. It was their single-shot model 179 BB pistol.

 

How fast do pellets go?

At the end of this article is a video that I filmed December 2008 at the LASSO (Long-range Airgun Silhouette Shooters Organization) shoot outside of Dallas, TX.

This subject is confusing for new airgunners because many modern air rifles and a few air pistols are advertised to have velocities they cannot achieve. I've been testing this phenomenon for many years--ever since Gamo brought their 1250 Hurricane to market. That rifle was advertised as achieving 1,250 f.p.s., and the .177-caliber rifle I tested actually reached 1,257 f.p.s. when shooting
RWS Hobby pellets.

The early years
My early tests were conducted in the days before the
Gamo Raptor PBA pellet and other non-lead lightweight pellets were available. At that time, all I had available were lightweight lead pellets and the RWS Hobby was the lightest of them.


When the lightweight pellets did come out, nobody said much about what they did for airgun velocity until Gamo started their campaign with their Performance Ballistic Alloy, or PBA. The Raptor pellet is made from PBA , which is some non-ferrous metal that casts well--probably a zinc alloy--and is plated with 18-carat gold. A .177 Raptor weighs 5.4 grains, so the lighter weight adds considerable velocity to a rifle over standard lead pellets that start at about 7 grains.

Gamo has incorporated this fact into their advertising and now lists the velocity of some of their air rifles with two different speeds--one for PBA and a second number for lead pellets. And that ad campaign was what started my investigation into pellet speeds.

I haven't seen it yet
I've never witnessed a pellet going as fast as Gamo (and now Benjamin) advertises. Gamo advertises their .177-caliber
Hunter Extreme at 1,600 f.p.s. when shooting PBA ammo. Benjamin advertises the Super Streak at 1,500 f.p.s. Benjamin doesn't mention a specific pellet, but since they manufactured the now-discontinued Silver Eagle hollowpoint that weighs only 4.8 grains and in my testing had always beat the Gamo PBA for speed, I assume they meant the Super Streak to shoot that.

The airgun forums are alive with talk of pellet velocities. Some say it's impossible for a pellet driven by air to exceed the speed of sound, which is around 1,100 f.p.s., at sea level. Others argue that speeds of well over 1,600 f.p.s. are very possible.

Parlor tricks
Before we go any farther, let me explain that it is entirely possible to trick an air rifle into shooting a pellet over 1,600 f.p.s. Introducing a flammable liquid, such as oil, into the gun's compression chamber will cause it to detonate, driving the pellet well past 1,600 f.p.s. But that would be the result of a chemical explosion, making the gun a firearm, not an airgun. Daisy made a .22 caliber round that had solid fuel bonded to the base of a bullet, and it was ignited by a spring-piston airgun mechanism. But that was a firearm and subject to all regulations governing firearms.

We're talking about airguns, not firearms. For that reason, we must rule out guns that use chemical explosions to achieve their velocity. That eliminates the Gamo Hunter Extreme and the Benjamin Super Streak. In tests I have conducted the fastest a Gamo Hunter Extreme was able to shoot with .177 PBA pellets was 1,395 f.p.s. The fastest the Benjamin Super Streak went was 1,323 f.p.s., again with PBA pellets.

The fastest I've seen
However, I have witnessed faster pellets. When I worked at AirForce Airguns, I had occasion to test all manner of guns and pellets, and one time I saw a 5.7-grain .177 caliber
Skenco Hyper-Velocity Lead-Free pellet go through the traps at 1,486 f.p.s. That's the fastest pellet I've seen to date that didn't involve an explosion.

Dennis Quackenbush and I have been discussing this issue for a long time, and in 2008 he decided to do more then just talk. He built a special smoothbore version of his Outlaw rifle and barreled it in both .25 caliber and .375 caliber. He made two smoothbore barrels for the gun--one in either caliber--and produced lightweight "pellets" made from Delrin, an engineering plastic. He shot his test gun through my Oehler chronograph at the 2008 LASSO big bore shoot, and I filmed the whole thing for this article.


The video tells the whole story, unfortunately the portion where the .25 caliber pellet was filmed was lost. However, the maximum speed for the .25 caliber, 7-grain Delrin pellet was 1,425 f.p.s.

The bottom line
You'll see in the video that the modified rifle owned by Big Bore Bob Dean shot a 15.5-grain Delrin pellet at 1,474 f.p.s. That's the fastest shot I have on record. I won't say that faster pellets are impossible, but so far my experience indicates that they don't happen.

What About CO2?


What about CO2?



What about CO2?
A plain look at an intriguing gun powerplant

Carbon dioxide, or CO2, has been used to power guns since at least the 1870s, when Frenchman Paul Giffard first used it in his 6mm and 8mm gallery guns. In Giffard's day, CO2 was such a novelty that those who bought his gun had to send their cylinders back to a central filling station. There were no places to buy the gas conveniently.

In the late 1940s, Crosman marketed whole shooting galleries to companies, as entertainment for their employees. These eight-gun ranges were much less costly than even a one-lane bowling alley, plus they went into much less space. Lunchrooms were converted to shooting galleries, and league shooting was sponsored by the company.


In the 1940s, Crosman adapted 4-oz. military CO2 bottles to their "Silent" pneumatic rifle, which is the gun that collectors now call the CG (compressed gas). They never sold them to the public. They were part of a shooting gallery marketing plan Crosman pursued for a few years after WWII. The guns came with a tank that hung straight down (as shown) and one that hung slanted to the rear. They were made in a proprietary .21 caliber as well as the more conventional .22. This was America's first CO2 airgun experience


The guns used for this sport were standard Crosman pneumatic rifles, converted to accept 4-oz. CO2 bottles that the company bought cheap as war surplus. These guns were never sold directly to the public, as the marketing campaign was centered on the sale of an entire gallery and not individual guns.

Today, these CG (for compressed gas) guns are collector's items, but the concept has been reborn in the Crosman AirSource guns. Shooters can now gas up their rifles with enough for more than 300 shots - something the all-day hobby shooters will love!

Crosman has now come full circle and is offering a bulk-filled CO2 rifle once again. This 1077 is adapted to use the new 3.2-oz. AirSource bottle, as well as conventional 12-gram powerlets. With the AirSource bottle attached, hundreds of shots are available. A valve permits removal while the bottle still has gas.
Before we move on, let's clear up a question. Is a CO2 gun an airgun? If you mean, does it use air to power the shot? If so, then, no - it's not an airgun. But, that's a very limited definition and few people adhere to it today. Instead, most folks accept the definition of an airgun being a gun that uses something other than burning gunpowder to power the shot. In that sense, yes, a CO2 gun is an airgun.

The Powerlet
Benjamin was making CO2 guns that used commonly available 8-gram CO2 cartridges called "Sparklets" as early as the late 1940s. Sparklets were commonly used in seltzer bottles, which were very much in vogue at that time.


After the CG guns, Crosman brought out a series of bulk-filled CO2 pistols and rifles that lasted into the mid-1950s. This .177 model 111 still has its original box, 10-oz. bulk tank and instruction manual. The gun was holding gas when I purchased it at a flea market!
Crosman was also making CO2 guns for general sale, but they were more like Giffard's guns, because they were filled from a separate 10-oz. bulk tank that had to be sent off to be refilled. Today, such guns are called bulk-fill guns, and they're still being made, though not by Crosman.

The small 8-gram cartridge known as a Sparklet is dwarfed by the more popular 12-gram powerlet from Crosman. Since Crosman invented the 12-gram size, the term powerlet now applies to all cartridges of that size, regardless of who makes them.
In the middle 1950s, a Crosman employee converted one of their bulk-fill pistols to take a new, larger 12-gram CO2 cartridge and the Crosman 150 was born. It's no longer made, but the proprietary cartridge still is - and it's known all over the world by the name Crosman gave it - powerlet!

Probably 95 percent of all CO2 guns made today use a 12-gram powerlet. Powerlets are produced all over the world, and the name has lost its direct ties to Crosman by such universal acceptance.

How many shots you get from a powerlet depends on how much gas the gun uses for each shot. A rule of thumb is that a sporting pistol will give about 50 to 60 shots and a sporting rifle will give 40 to 50 shots. The exceptions to this rule are strange guns like the Czech APP 661, which has a very restrictive valve and gets over 100 shots at about 225 f.p.s.



CO2 and Pressure
CO2 is a gas at temperatures above -69.9 degrees F and 60.4 psig (pounds per square inch gauge). It is a very complex compound with the ability to sublimate (change directly from a solid to a gas without becoming a liquid) as just one of its unique properties.

At 70 degrees F, CO2 obtains a gas pressure of 852.8 psi when confined in a vessel. If there is more CO2 in the vessel, it will be have to be in liquid form. So, the state of CO2 in a pressure vessel, such as a powerlet at room temperature, is a pressurized gas above a liquid. If the gas is released, such as through the operation of an airgun valve, some of the remaining liquid flashes to gas until the pressure is equalized for that temperature.

It's important to understand that CO2 pressure is determined by temperature, not by mechanical compression. If you were to compress gaseous CO2 by mechanical means, it would turn into liquid when the right pressure was reached. The pressure in a 12-gram powerlet remains constant until all the liquid is gone. A powerlet has the same internal pressure as a 10-oz. bulk CO2 tank when both are at the same temperature. Therefore, CO2 guns do not lose velocity as you shoot them until all the liquid is gone and they start to run out of gas.

Also, keep in mind that CO2 is a refrigerant gas. That means it cools when it expands by flashing from liquid to gas. Therefore, when you shoot a CO2 gun rapidly, the gas will cool the gun parts considerably. Because CO2 pressure is based on temperature, the pressure in a CO2 gun will drop if a series of shots are fired in rapid succession. In practical testing, I've seen velocities decrease by more than 100 f.p.s. over a long string of shots. That will affect where the pellet strikes the target unless it's very close to the shooter. So, if you want to shoot accurately with a CO2 gun, do not shoot rapid-fire. With a target pistol, I like to allow at least 15 seconds between shots so the gun's temperature can cycle back to where it was before the shot. But, if you're just plinking, you can shoot faster than that.

DOT regulations require the use of a burst disk in pressure vessels larger than two inches in diameter. The brass nut with the hole in the side contains the burst disk in this bulk CO2 tank. If pressure inside the tank rises above the safety level, the disk ruptures, releasing all the gas inside. That keeps the entire bulk tank from exploding with the force of a bomb.
On a very hot day, CO2 pressure will climb rapidly into the danger region. Where that danger region is, depends on how much liquid is in the pressure vessel. Larger CO2 tanks have pressure-relief devices for safety; so, instead of the whole tank blowing apart like a hand grenade, the burst disk will rupture and exhaust all the gas. When this happens, it's very startling to anyone nearby, and the tank has to be repaired before it will hold CO2 again. Obviously, it's unsafe to leave a CO2 gun or a tank in a closed car on a hot day.

How fast does my gun shoot?
With some types of airguns, this can be difficult to answer without actually measuring the shots with a chronograph. But, with CO2 velocity depends on just a few variables. With experience, you can estimate how fast a CO2 gun will shoot accurately just by knowing a few things. A short barrel shoots slower than a longer one. A pistol with a 4" barrel will shoot between 250 and 375 f.p.s. Since there's no easy way to increase the pressure and there's not enough barrel length to use the extra pressure even if it could be increased, this range describes most guns pretty well. A pistol with a 5" barrel will get around 400 to 500 f.p.s. in .177 and 350-450 f.p.s. in .22.

Umarex, the company that owns Walther of Germany, makes several realistic CO2-powered copies of famous firearms. The S&W 586 revolver will shoot faster than the Walther CP88 pistol because it has a longer barrel.

In a .177 rifle with a 20" barrel, 675 to 750 f.p.s. is common. In .22-caliber with the same 20" barrel, 575 to 675 f.p.s. is common. I've seen some .22-caliber Philippine CO2 rifles with slightly longer barrels get over 900 f.p.s on a very hot day, but on a milder day (less than 85 degrees F) they shoot in the low- to mid-800 f.p.s. range. These guns have wide-open valves and were built to shoot as fast as possible. By wide-open valves, I mean that the orifice through which the gas flows is as large as it can be and the valve's return-spring is balanced against the weight of the hammer and the power of the mainspring to hold open the valve as long as possible.
The key to higher velocity with a CO2 gun is both high ambient temperature and a long barrel. And, this type of powerplant usually does much better in terms of raw power with the heaviest pellets. That also means that .22 caliber is preferred over .177 when power is needed.


CO2 facts


1. CO2 guns do not lose velocity as they shoot.
The first two or three shots will be faster because some of the liquid CO2 is blown into the firing valve and expands there or in the barrel, increasing the density of the gas charge. After that, you get a long string of shots at the same velocity. The only thing that can reduce velocity during this string is rapid fire shooting, which cools the gun. Slow down to allow the gun to warm up, and the velocity will pick up again.
At the end of the liquid CO2, the remaining pressure will begin to drop rapidly and velocity will start going down. After that, velocity will decrease until the gun is recharged or a new powerlet is installed.

2. CO2 guns will not operate well with other gases. To operate correctly, a CO2 gun needs a constant pressure level around 900 psi. Only CO2 will give that pressure at room temperature. Also, the valve's dwell time for a CO2 gun is MUCH longer than for an airgun running at a similar pressure, because the carbon dioxide molecule is so much larger than any of the gas atoms found in air. If you were to pressurize a CO2 gun to 900 psi with regular air, you would get one or possibly two powerful shots, then the velocity would drop off rapidly. Air, being much thinner, flows through a valve faster, which gives higher velocity until the pressure drops off.

3. Some CO2 guns require the removal of their powerlets after shooting.
And, some don't. I've shot CO2 guns that had been charged with gas for at least 20 years and they still shot like new. The time a gun can stay charged depends on its design and construction. Follow the manufacturer's recommendations at all times.

4. A CO2 gun depends on its seals to hold in the gas. Most of those seals are O-rings of some kind. O-rings need a thin film of oil to do their job, and they like silicone oil the best. Silicone oil for this purpose is sold by
Crosman, Daisy and Gamo.

5. CO2 pressure - and, therefore, velocity - depends on temperature.
When the weather is warm, the gun shoots faster. Shooting indoors on a cold day allows you to shoot during cold weather.

6. Barrel length determines velocity to a great degree.
In this respect, CO2 acts exactly like black powder. Both need time to do their thing, and the longer the barrel (to the point of diminishing returns), the faster they shoot.
7. A powerlet and a large CO2 tank have the same internal pressure at the same temperature.
This is a difficult concept to grasp, but it's the reason CO2 powerlets are such a wonderful power source. They hold enough liquid for many shots, yet they're small enough to be very handy.

8. A CO2 gun cools when shot rapid-fire, which means lower velocity.
There is no way around this. You have to let the gun warm up for a few seconds between shots if you want a consistent velocity level.

Pellets vs Round Balls 

How do pellets perform compared to round balls?


There is a controversy concerning the performance of pellets and round lead balls that has been around for more than a decade. The round ball advocates tell us that round lead balls out-penetrate lead pellets by a dramatic margin. A second concern has to be relative accuracy. We already know how accurate certain lead pellets are - if the round ball cannot keep pace with them, any extra penetration is a moot point. You have to hit what you shoot at, first of all.

TEST ONE - PENETRATION


To resolve this question, I decided to conduct a simple test: Shoot both pellets and round balls into a transparent medium and see which penetrates the best. The medium is one I have used in the past. It's a Neutrogena facial bar, and it's large enough to absorb hits from air rifles up to about 15 foot-pounds. No claim is being made that Neutrogena soap resembles animal flesh in any way - this isn't a test for that. It's simply designed to measure the relative penetration depths of different projectiles in a standard medium. The density of the bar will give a good comparison of the projectiles while not allowing them to shoot completely through. The fact that it is transparent allows us to see the relative penetration, side-by-side, without distorting anything by cutting the bar open. This test will be conducted in .177 caliber only. That may seem limited to some shooters, but the relative penetration characteristics should remain the same regardless of caliber. The test should also hold for both high- and low-powered rifles. But, just to be sure, I'll use one of each. A CZ 631 breakbarrel will be the low-powered gun and a TX 200 will be the high. Since this test is about penetration, we are also testing a pointed pellet with the other two projectiles. A lot of folks think that the pointed pellet's shape gives it an advantage in penetration, so this test should prove once and for all who is right. To keep the test as fair as possible, I tried to use pellets and balls of similar weights. A round .177 ball weighs 8.7 grains and there isn't much that can be done about it. For the ball to be heavier, it has to increase in size, which will make it too large to shoot. Pellets, on the other hand, can be made either long or short with skirts that are either thick or thin. A .177-caliber lead pellet can be as light at about 6.5 grains or as heavy at 11.5 grains. That's a pretty wide range and the heavier pellets will have more momentum, which means more penetrating power. So we kept the weights relatively close for all three projectiles.

Conducting the penetration test
The Neutrogena bar is laid on clean paper inside a steel Outer's bullet trap. If any pellet escapes the bar, it would have nowhere to go but into the trap. The muzzle of the rifle is held against the bar for every shot. The barrel is held so that the flight of the pellet will be as centered in the bar as possible. Any angularity might allow the pellet to escape the bar, especially when the high-powered rifle is used. Also, I wanted the paths of the pellets to be as close as possible to parallel with each other.

Before the first shot is fired, each rifle is fired five times to bring the piston seal up to optimum performance. From experience with hundreds of chronograph tests, I know that this is adequate to get the rifle performing as it should.


From left to right are the three pellets tested: a Chinese domed pellet weighing 9.1 grains, a Gamo round ball weighing 8.7 grains and a Beeman Silver Jet weighing 8.7 grains.



No doubt about it - round balls do penetrate deeper than domed or pointed pellets shot from the same gun. These were all fired from a CZ 631 rifle with the muzzle less than one inch from the soap bar. Notice that the round ball in the center has left a smaller channel behind it, which is the secret to deeper penetration. The pointed pellet on the right has also penetrated slightly deeper than the domed pellet on the left.

Here is the telling photo! The TX 200 is more than twice as powerful as the 631, so the margin of the round ball is even more dramatic. It has passed completely through the soap bar, leaving an exit hole as well. The pointed pellet on the right is also pulling ahead more visibly in this photo, though the margins between all three projectiles remain the same from gun to gun.
The photos leave no doubt about it - round balls do penetrate deeper than domed pellets and pointed pellets. The reason is seen in the narrow wound channel left behind the ball. It looses energy at a slower rate than either of the pellets, making it less desirable for thin-skinned animals like chipmunks and small birds. But if you really need penetration on tough animals like crows and larger mammals, round balls may be the way to go. The bar was not restrained in any way. Hits from the CZ 631 moves the bar by several inches; the TX 200 slams it clear back into the back plate of the bullet trap, except when the round ball passes completely through.


TEST TWO - ACCURACY


I also shot all three projectiles in both rifles at about 15 yards. This shows the relative accuracy, but the results are not what you think. Instead of ruling out the round ball completely because it isn't as accurate as a pellet, you can establish the range at which you can hold a group sized to the kill zone of your quarry. For a crow, that might be 1.5 inches. For chipmunks, it's an inch or less. The distance at which you can hold a five-shot group that tight is the range at which a projectile can be used.


The Chinese pellets (left group) and the Silver Jets (right group) were a little tighter than the round balls. Shot at 14 yards from a standing orted

Chinese pellets on the left and Silver Jets on the right. Shot standing supported at 14 yards with a scoped TX 200. In this rifle, the round balls did quite well.



CONCLUSION


Round balls out-penetrate diabolo pellets. They can be as accurate as most diabolos in some airguns. Use them on hard targets, where penetration is desired over energy transfer - and hold your maximum range to the distance at which you can hold a group in the kill zone of your quarry.

Velocity and Pellets 



 

Velocity - Accuracy - Value
Some things to look for in an airgun


 



 
VELOCITY AND PELLETS


It seems fantastic that an air rifle can launch a pellet faster than 1,200 feet per second (f.p.s.), but some powerful rifles can. However, just because it's possible to do it doesn't mean that it's also desirable. In fact, it isn't. To understand why, you must understand how a modern pellet works.

Diabolos


The classic diabolo pellet has a pinched waist and a hollow skirt. The shape of the nose can be round, pointed, flat or anything else. The skirt can be thick or thin - long or short. All these variables affect the flight of the pellet somewhat, but the basic diabolo shape is what affects it the most. These .22-caliber Benjamin-Sheridan pellets are very similar to Crosman's Premier design.
Most top-quality pellets are made with a pinched waist - a so-called wasp waist. The correct term for this design is diabolo. A diabolo pellet is stabilized (prevented from tumbling) by the high air drag on its tail. A hollow skirt plus the pinched waist work together to produce this drag, plus a forward weight bias keeps the nose pointed in the right direction. Where a conventional rifle stabilizes the bullet by spinning it rapidly, a diabolo pellet will even be reasonably accurate in a smoothbore gun. It works exactly like badminton "birdie" and for the same reason - a high-drag skirt. Most modern pellet rifles and pistols are rifled which does cause the pellet to spin on its axis in flight, but the rate of spin is too slow to stabilize the pellet by itself. When the pellet leaves the muzzle it starts slowing down very rapidly. It will lose more than half its muzzle velocity within the first 100 yards of flight. If the pellet was shot at a speed above the sound barrier, it will also be destabilized by passing through the sonic pressure wave it created. The sound barrier varies, but it usually remains near 1,100 f.p.s. at sea level on a normal day. When a pellet goes faster than the sound barrier it makes a sharp crack, which is the "breaking" of the barrier. It will be less accurate than if it were shot from the same gun at 900 f.p.s. or less, where the sound barrier is not a problem. While 900 f.p.s. is quite a bit below 1,100 f.p.s., there is great turbulence whenever the sonic barrier is approached. For this reason, knowledgeable shooters never allow their pellet rifles to shoot much faster than 900 f.p.s. If they buy one of the supermagnums that do shoot much faster, they use the heaviest pellets they can find to get the muzzle velocity back down.


Match King Boat Tail
Missiles that travel faster than the speed of sound slow down much faster than missiles going slower than the speed of sound. To retain their velocity, supersonic missiles must be very aerodynamic, while slower missiles are less aerodynamic.

On the low end of the scale, Olympic target airguns seldom shoot pellets as fast as 600 f.p.s., yet they will outshoot almost any other pellet gun at short ranges. The target air pistols are nearly as fast as the target rifles - ranging from 450 f.p.s. to 580 f.p.s. Both target rifles and pistols shoot wadcutter pellets with flat noses that cut perfect holes in target paper. Wadcutters are the least aerodynamic pellets on the market, but since the target guns don't shoot very fast, it doesn't matter. Most hunters want a rifle that will shoot a large heavy pellet accurately at 750 to 900 f.p.s. Most general shooters - the so-called plinkers - want to shoot at 600 to 900 f.p.s. with a rifle and 350 to 550 f.p.s. with a pistol. High velocity does not mean high quality or accuracy. If fact, it might mean just the opposite. The diabolo pellet is designed to give the greatest accuracy at speeds well below the sound barrier, so select your airguns accordingly.
The boattail pointed bullet is designed for supersonic flight at all times. This is a Sierra MatchKing, which is one of the top target bullets in the world. It is made of a copper jacket around a lead core with a tiny opening in the point. They come in all popular calibers, but this .30 caliber 168-grain bullet is what made the line famous. It's used for long-range target shooting, primarily.


WHAT ABOUT SOLID PELLETS?


Okay - if hollow-tail wasp-waisted pellets aren't accurate above the sound barrier, what about solid lead "pellets?" Several brands of these interesting "pellets" are now available, but do they give the accuracy you require? Another name for these solid pellets is bullets, because that's exactly what they are. So what works for bullets also works for solid pellets.


These are both .22-caliber pellets. The 30-grain pellet on the left is a solid lead pellet from PelletMan. The lack of a hollow skirt and a wasp waist means this pellet has to spin faster to stabilize in flight. Than means it must be shot faster than a normal pellet. It has a cupped base, plus there is a larger-diameter driving band around the base to take the rifling and seal the bore. The Crosman Premier diabolo on the right weighs 14.3 grains.
As it turns out, .22 long rifle ammunition, which fires a 40-grain lead bullet, is ALSO less accurate if the bullet goes supersonic. Why? Because when it is just barely supersonic, as most .22 LR high-speed ammo is, the bullet gets tossed around by its own sonic wave. To get around this, a bullet has to be extremely streamlined and it needs to be shot at several times the speed of sound. So, if you can get your solid pellets out the muzzle at 1,400 f.p.s. and faster, there may be an advantage. Less than that and you are tossing away accuracy. That's why all .22 rimfire target ammo is subsonic. Learn from the target shooters and stay well under the sound barrier. If you do shoot solid pellets, remember that they must go faster to stabilize because they don't have the high drag of the hollow tail. The spin imparted by the rifling must stabilize them.


BUT DOESN'T A FASTER PELLET DROP LESS ON ITS WAY TO THE TARGET?


Yes, it does. It also wanders all over the place instead of tracking along an accurate path. So you can either hit your target with the slower pellet or you can miss it with a faster pellet that doesn't drop as much - it's your choice. Back in the late 1800s, men shot at 1,000 yards and even out to one mile with bullets that barely went supersonic, if at all. They had to judge the range more than shooters do today, but their rifles were very accurate. The bullet that hits the target does more damage than the one that misses at high velocity.

SO, ARE THE SUPERFAST AIR RIFLES BAD?


Not at all! They're great - especially if you need extra power for hunting and long-range shooting. But use them correctly. Match their high power with heavy pellets so you get all the accuracy they have to offer. For example, a Gamo 1250 will shoot over 1,200 f.p.s. in .177 caliber with the lightest pellets. RWS Hobbys weigh about 6.9 grains and Skenco lead-free pellets are more than a full grain lighter. You would not use them in a 1250 because they are too light. Instead, use a Beeman Kodiak/H&N Barracuda (same pellet) that weighs 10.6 grains or a Crosman Premier 10.5-grain pellet. These will both slow the velocity down to somewhere in the 1,000 f.p.s. region where the rifle can do its best. If you have a choice of calibers, such as with the RWS 350 Magnum, which comes in both .177 and .22, get the .22 and use the heavier pellets. You will get all the smashing power the powerplant has to offer. If you absolutely must have a .177 in one of the super-powerful rifles, always match it with the heaviest pellets for the caliber.

CONCLUSION


Airgun quality does not come from velocity. It comes from accuracy, smooth operation, good design and quality control and other factors. Don't allow velocity alone to rule your airgun choices because if you do, you will miss most of what is good about this hobby.

MUZZLE ENERGY and VELOCITY

Want to know how it works?
Multiply the product of the weight of the pellet (in grains) times the square of the velocity and divide that number by 450240. That last number is a constant created by multiplying two times the acceleration of gravity by 7,000 - the number of grains in a pound. The number I am using for the acceleration of gravity is 32.16 f.p.s. That number is obsolete, but the number that replaces it, 32.174 feet per second (f.p.s.) below the 50th latitude, does not change the energy calculation significantly.
Here's how the formula works. Suppose we shoot an 8-grain pellet at 800 (f.p.s.). The energy would be 8 times the square of the number 800, which is 640,000. So, it's 8 times 640,000 - which is 5,120,000. Now, divide that number by the constant 450240 and you get 11.371712. There may be even more digits out to the right of the decimal point, but that's where my small calculator stops, so that's my answer. I'm going to round off the number to two decimal places anyway, so I write it down as 11.37 foot-pounds.
The problem above looks like this when written in mathematical notation:

What do I care what muzzle energy is?


You may not care, and it's OK! However in many cases when you read an airgun specification you may see only muzzle energy indicated or only muzzle velocity. While for some people it's irrelevant to some people it matters. For instance some country laws may prohibit ownership or import of air rifles above certain muzzle energy.

For pellet weight: grain and velocity: ft/sec foot-pounds or joules

Remember to multiply all the numbers above the line before dividing the answer by the number below the line.
671 - the magic number


A velocity of 671 f.p.s. for any projectile gives the same energy number in foot-pounds as the weight of the projectile in grains. For example, an 8-grain pellet traveling 671 f.p.s. generates 8 foot-pounds. A 20-grain projectile going 671 f.p.s. generates 20 foot-pounds and a million-grain (142.86 lbs.) projectile going 671 f.p.s. generates a million foot-pounds. A 3,000-lb. automobile going 671 f.p.s. generates 21 million foot-pounds, which is why we should be glad not too many cars ever go that fast.

The magic number is helpful when you have projectiles going near that velocity. For example, many big bore airguns shoot about that fast, so all you need in order to determine their energy is look at the weight of the projectile they shoot in grains. If someone tells you that his big bore .50-caliber rifle shoots a 180-grain lead ball at 700 f.p.s. and gets 500 foot-pounds of energy at the muzzle, you can now determine in your head that he is wrong. You may not be able to calculate the correct number in your head, but it's going to be a lot closer to 180 foot-pounds than to 500 foot-pounds.


If you know the energy, how do you find the velocity?
The quick way to find the answer is to work a reciprocal of the energy formula; but, if you're like me, you need to be reminded how that's done.

Take the energy times the constant 450240 and divide by the weight of the pellet in grains. The square root of that number is your velocity.

Let's find the velocity of an 8-grain pellet that generates 11.37 foot-pounds of energy. That would be 11.37 times 450240, and divide that number by 8. Then hit the square-root key on your calculator.
If you know the energy, how do you find the velocity?

Airgun energy foot-pounds and pellet weight: grain ft/sec


My calculator comes up with 799.93974, which is pretty close to 800. Remember, we rounded off the energy number, which accounts for the small difference between our answer and the number 800.


Summary

You can shoot airguns a lot without ever getting into the numbers like these, but since a lot of advertising is based on numbers, you now have a way of decoding what they are saying.

 

MUZZLE ENERGY and VELOCITY: Continued

What do advertised airgun velocity numbers mean?

Airguns are usually advertised with their expected top velocities. What do those numbers represent? Today, I’ll attempt to explain this as clearly as I can.

The numbers are just lies!
Let’s get this one out of the way first because it seems to be the prevailing belief that advertised velocities are nothing but lies put forth by marketing departments to sell more guns. There’s some truth to this belief, but it isn’t 100 percent by any means. Here’s what’s going on with the lies.

In the 1970s, spring-piston air rifles broke the 800 f.p.s. “barrier” for the first time. Three guns — the BSF S55/60/70, the Diana 45 and the FWB 124 all topped 800 f.p.s. in .177 caliber…and the HW 35 came very close to 800. That started the velocity wars that are still with us today. In 1981/82, the Beeman R1, which was also produced as the HW 80, hit 940 f.p.s. in .177. A year later, it was hitting 1,000 f.p.s. right out of the box, and that became the new standard for magnum airguns.

A couple years after that, Diana offered 1,100 f.p.s. with their sidelever models 48 and 52, and from that point on it was necessary to go even faster to gain recognition in the air rifle class. A thousand feet per second was now considered the lowest velocity a magnum airgun should achieve in .177 caliber.

Then, Gamo upped the ante with their 1200 Hunter Magnum that became the 1250 a year after it was introduced. This was in the late 1990s, and I was writing The Airgun Letter, so I obtained a 1250 from Gamo and tested it for myself. To my utter surprise, that test rifle achieved 1,257 f.p.s. with an RWS Hobby pellet. I thought the game was finally over. Boy, was I mistaken.

Within five years, air rifles started hitting the market with claims of over 1,300 f.p.s. And then they bumped up to 1,350 f.p.s. You could almost hear the various marketing departments discussing what they had to say in order to sell their next new magnum air rifle. But when I tested these guns, they fell short of their advertised marks. I was not quiet about that fact; but when the box on the store shelf says one thing and I say another, guess which one people believe?

The numbers kept right on climbing — up past 1,400 f.p.s., then 1,500 f.p.s. and finally stopping at 1,650 f.p.s. I’ve also tested many of these newer rifles; and while they often do achieve velocities that used to be impossible, like over 1,300 f.p.s., none has ever hit 1,500 f.p.s. without some kind of fuel-air explosion being involved. The fastest velocity I’ve ever recorded from a spring-piston air rifle was just at or under 1,400 f.p.s., and one person reported he had achieved a legitimate velocity of 1,425 f.p.s. I’m talking only about spring-piston air rifles now, because a .177 AirForce Condor has hit 1,486 f.p.s. in one of my tests.

Non-lead pellets
While all these velocity claims were stacking up, the market was also flooded with lead-free pellets. Being lighter than lead pellets, these pellets went faster at the muzzle. The fact that they could not carry that velocity very far downrange was lost on the majority of people. One ambulance-chaser “expert” witness in a wrongful airgun death lawsuit went so far as to compare a magnum air rifle pellet to a .22 rimfire bullet fired from a handgun. He “demonstrated” on television that the airgun was faster than the firearm with no mention of the effects of a lightweight pellet compared to a 40-grain bullet. Well, a neutrino travels at nearly the speed of light and passes through the earth unresisted; but since it has almost no mass, it doesn’t do any damage. Velocity alone means little.

That is the story of the velocity claims for pellet guns that are either outright lies (where the actual number you can achieve without resorting to some trickery is lower than the claimed velocity) or are stretching the truth beyond credibility (where ultra-lightweight pellets are used to obtain the number).

Legal concerns
This issue is the one I believe many folks do not consider when they focus on velocity claims that seem unrealistic. While we would never consider shooting a lead-free 5-grain pellet in a magnum air rifle, or in almost any air rifle, for that matter, there’s a reason to do it. Some communities and states have laws specifying the maximum velocity an airgun can legally achieve. If it exceeds that — well, the outcome isn’t clear because these laws are written in many different ways.

In one jurisdiction, the law may set an absolute maximum velocity for the airgun. No projectile weight is usually given in such a law, so if any pellet can exceed the maximum, the gun is not legal there. Working against such laws are the companies that make plastic airgun pellets weighing 3 grains or less. They will scream out of the muzzle and through the chronograph before slowing down as though they are tethered to the gun! Such pellets may bring a smile in certain places, but they can bring down the law in other places that have maximum velocity laws. The only thing that has kept many airguns safe so far is the general lack of knowledge that such pellets exist.

In another community, the law may include both a velocity maximum and a maximum muzzle energy. This law can be written two different ways. One is if the airgun surpasses either maximum it violates the law. The other way the law can be written is that the airgun must surpass both criteria before it violates the law.

Airgun manufacturers do not know all the laws that are in force. There’s no way they can because new laws are written all the time, and existing laws are modified or clarified to change their impact. In a country like the United Kingdom, where the law is relatively straightforward — keep the muzzle energy under 12 foot-pounds to stay legal as an airgun, the manufacturers have a parameter they can build to. But in a country like the United States — where airguns are totally unregulated in some places and highly regulated in others, a manufacturer stands little chance of remaining abreast of the law.

They do their best to comply with the laws they know and hope that companies like Pyramyd Air, who sell their products, will stay on top of things, too. They (the manufacturers) watch the big trends and try to tailor their products to those, and they trust their dealers to know the market they sell to.

Edith serves in this capacity for Pyramyd Air. She monitors state and local laws, and she calls the attorney general of any jurisdiction or state authorities if she finds the laws have changed or are going to change. Sometimes, she gets solid answers that can be trusted, but other times she discovers that the people in charge are not aware of how to interpret their own laws.

One example of this was in a Midwestern state that we won’t name to spare them embarrassment. Edith was unable to get an answer to a question about a law. She spoke to person after person in that state’s division that regulates guns. One time, she ended up speaking to a woman who was the head of the entire division because she’d gotten 5 different interpretations from 5 different officers. During the conversation, the head of the division mentioned that the ATF regulates all .50-caliber guns so the state didn’t have to regulate .50-caliber airguns. Of course, Edith explained that .50-caliber airguns are sold coast to coast in the U.S. and, except for a few states, are totally unregulated. Nothing she said could convince this woman. After all, Edith was just some person calling this police authority, so how could she know better. Sometimes, it’s impossible to counter ignorance.

Company velocity criteria
Some airgun manufacturers categorize their guns by the velocity they produce. Daisy is one that does. They have youth products separate from their Powerline products. They recommend their Powerline products for shooters 16 years and older. I searched the Daisy website looking for the velocity break between a youth gun and a Powerline gun but didn’t find a number. But looking at what the Powerline models deliver, it looks like it’s any gun capable of shooting faster than 600 f.p.s. in a long gun and all handguns. There’s also the Avanti line, which is for target shooting; and, while all the long guns shoot under 600 f.p.s. and are considered youth models, there are 2 pistols in the Avanti line and the Powerline designation is in their model names.

What does this mean to an airgunner?
An airgunner has no way of knowing the meaning of the velocity number that’s given with a particular airgun. It could be for bragging rights, or it could be the fastest velocity the company engineers were able to obtain from the gun under controlled conditions. They could be using the number to sell more guns to uneducated shooters, or they could be using it to segregate their products for sales to different jurisdictions.

Company A tests all their guns with real-world lead pellets that shooters might also use. AirForce Airguns is one such company, and they even tell you what the test pellet is (a Crosman Premier pellet of the appropriate caliber, by the way). Company B is run by the marketing department, and they inflate the velocities of their magnum line of rifles and pistols by 10 percent. I’ve had executives in these companies tell me they did this because — to use their own words — “Everyone else does it, so why shouldn’t we?”

Company C uses the lightest pellets they can find to test their guns, so they don’t run afoul of those places where velocity, alone, is the criteria. And so it goes. This is why it’s impossible to know what the velocity figures mean unless you know the company that publishes them and their policies.

And the answer is…
The answer is — there is no one answer. Airgun velocity is a complex topic that’s driven by forces both within and outside the company making the guns. This is where the budding airgunner has to become a thoughtful researcher when looking for a certain gun. Pyramyd Air tries to post the most correct velocity for each model, but they’re at the mercy of both the airgun manufacturers as well as the makers of pellets.

Experience is the best guide when it comes to this topic. With experience, you’ll know what the limits are, which companies do what with their numbers and so on. But never think for a moment that all published velocities are incorrect.

 

 

 

“This may be a dumb question — but, since the issues revolves around the ‘badminton birdy’ design of our current air rifle pellets. Has there been any attempts to change the design to provide stable flight, and maintain more energy, at faster speeds? Just curious….”

That is not a dumb question at all! In fact, it’s such a good and thoughtful question that I thought it deserved a special report because we’re seeing a rise in the number of firearm shooters who are reading this blog. Just like airgunners, those who shoot firearms come with different levels of experience; and some of them are not attuned to the fundamentals of accuracy. They buy commercial or military surplus (milsurp) ammo and just shoot it without appreciating how much better they might do with a little tweaking.

The same can be said of airgunners, many of whom have bought into the high-velocity craze without realizing (or perhaps caring) all they are giving away. Today, I want to look at the projectile we shoot — the common pellet — with the hope that, by understanding its design and limitations, we can extract the best our airguns have to offer.

The diabolo pellet
Diabolo (pronounced dēˈabəˌlō). According to the dictionary, the origin of the word comes from a toy top that was popular in parts of Europe. It was also sometimes used in juggling performances. The word came from 20th century Italian from the ecclesiastical Latin diabolus, which means devil; the game was formerly called devil on two sticks.

The diabolo pellet is characterized by a pinched or wasp waist and a flared hollow tail or skirt. Though there are many different variations on this central theme, they all have these characteristics.


The diabolo pellet can have different nose shapes, but all of them have a pinched waist and a flared hollow tail. The center of mass is biased forward by the hollow tail.

The design of the pellet biases the center of mass forward of the center point, like a throwing dart. The flared skirt and to a lesser extent the pinched waist create high drag that keeps the pellet oriented forward in flight.

History
I wish I could say exactly when the diabolo pellet was first introduced, but I’ve been unable to find a source that gives a definitive date. Nor is there a George Diabolo after whom the pellet is named. What I can say at this time is that it didn’t exist in the 1880s but was already in existence when the first modern air rifle — the Lincoln Jefferies underlever made by BSA — was offered in 1905. That’s as close as I’ve been able to pin down the date of introduction. I would welcome any information that contradicts my dating or offers greater insight.

When the diabolo pellet was first sold, most airguns were smoothbores whose designs were already many decades old. Buglespanners, the underlever guns that cock via the triggerguard, were being made in calibers as small as .22 as early as the 1850s, though that caliber is rare. By the mid-1870s, a great many companies were selling smallbore airguns in many calibers.

Perhaps the most well-known and prolific of these, at least in the United States, is the Quackenbush company, whose proprietary .21-caliber long guns and pistols sold for a tenth the price of handmade gallery airguns from just a decade before. Quackenbush guns and the others like the Gem, Haviland and Gunn, and others all used darts and something called cat slugs (sorry, Edith) that were nothing more than cylindrical lead slugs of bore diameter. They were very short, so they either avoided the tendency to tumble or it didn’t matter that much. Another variation of the cat slug was the felted slug, which was a cat slug with a short wad of felt clued to the base to provide drag.

Once the diabolo pellet came on the scene, it quickly rose to the top of the sales heap, surpassing all other projectiles. It did so because its high-drag design stabilized the flight of the pellet without requiring a rifling-induced spin. However, spinning the pellets did much to improve their accuracy, and the new BSA spring guns could not have hit the market at a better time.

Where the other types of projectiles were inaccurate at distances beyond 30 feet (excepting some handmade darts that were extremely accurate and had been in existence for over a century, but required specialized and expensive dart guns), the new diabolos pushed out the distance to 60 feet, where they gave one-inch, five-shot groups. In that day, being able to group like that was like saying a modern PCP can group an inch at 200 yards. It was an unthinkable distance that revitalized airgunning like nothing before.

Diabolos and the accuracy barrier
Certainly, up to this point in time (1905), there had never been any thought given to airgun projectiles going faster than about 500 f.p.s.; and only that fast in very few guns in the smallest caliber (No. 1 bore, which is also called .177). Velocity was not important, as the airgun was seen as an extension of the gallery target gun — though one that was much less expensive and more available to the common man. Accuracy was the sole purpose for the diabolo until the mid-1920s, when the Crosman Corporation started selling a hunting-themed pneumatic (Power Without Powder).

Power/velocity in airguns crept up very slowly throughout the 1920s and ’30s, and accuracy did the same. What held back accuracy was not the barrels of the guns, some of which were very fine, but the quality of the pellets. Airguns had run into the “accuracy barrier” because the manufacturing processes hadn’t reached the levels they would several decades later. It wasn’t until after World War II that European pellet makers finally started making really accurate diabolo pellets.

Sheridan shows us the way
In fact, there’s an anecdote in all of this; because in 1947, the Sheridan company decided to not use a true diabolo design and instead created a proprietary cylindrical pellet that had no pinched waist but did still have an open tail. The tail was not flared; instead, it had a tiny stepped ring of lead that was slightly larger than the diameter of the rest of the pellet and that was what was engraved by the rifling when the pellet was loaded.


The vintage Sheridan cylindrical pellet was not a true diabolo, but it had high drag just the same.

The reason given for this departure was that there was no accurate .22 pellet available. That may have been the truth, because the first prototype Sheridan rifles were created in .22 caliber; though, when brought to market, they came in a proprietary .20 caliber that has been the same ever since.

The first Sheridan pellet was a throwback to the schuetzen rifle days when all lead bullets were made with bases that were a couple thousandths larger than the rest of the bullet. These bases sealed the bore against the hot gasses at firing, and they also made it possible for the shooters to load the bullets separately into the rifled bore ahead of the cartridge case. This prevented the bullet from tipping as it entered the bore, because it was already seated there by hand.

The one or two lead rings at the base of the bullet were relatively easy to engrave with the rifling, as opposed to trying to engrave the entire bullet. That was the mistake that British and German pellet makers made when they tried to make the solid pellets (which I’ll discuss in a moment).

The sound barrier is breached!
Until the 1980s, peak pellet velocities remained below about 870 f.p.s. In the early ’80s, several rifles finally achieved 1,000 f.p.s. Soon after that, British airgun designer Ivan Hancock broke the sound barrier with his Mach I breakbarrel springer that got over 1,150 f.p.s. in .177 caliber. After that, things changed very fast.

Suddenly, accuracy was out the window, as shooters discovered that the diabolo shape is not well-suited to flight in the transonic or supersonic region. The fact that the pellet remains at this high velocity for only a few yards makes no difference. The damage was done. The extreme buffeting caused when the pellet reaches and passes transonic speed, then slows back down and goes through it again is more than enough to destabilize it and cause groups to open.

Sales go crazy!
However, the other side of the coin is that high velocity sells guns. A company that advertises their gun shoots 1,000 f.p.s. and higher attracts lots of attention and, yes, sales. In fact, so much attention has been given to 1,000 f.p.s. that it is now seen as the marketing kiss of death to advertise anything less. Some companies have gone to great lengths to tout ever-higher velocities without a thought being given to accuracy. Special lightweight, lead-free
pellets are now selling well partly because of the velocity boost they give to the guns that shoot them.

Which brings us back to the initial question
If the diabolo design doesn’t work at high velocity, and we know unequivocally that it doesn’t, then why doesn’t someone design a pellet that can exceed the sound barrier? Well, to a very limited extent and with disastrous results, it has been done. The so-called “solid pellet” was the first attempt to do this. This projectile is really a bullet — not a pellet, and as such is brings all its bullet weaknesses with it. The first is that nobody can load a lead bullet into the bore of a rifled gun unless he’s Superman. Those who shoot muzzleloaders know that it takes a device called a short starter and often a separate mallet to force the bullet into the rifling of a bore.


These .22-caliber Eley solid pellets weigh 30 grains and require the shooter to engrave the rifling at loading. They failed because they’re too difficult to load and because they’re inaccurate in most airguns. Other designs were similar and have had the same problems.

So, no solid pellet currently on the market can be loaded into an airgun easily enough to use. If it could, the second problem crops up. The twist rate of the rifling is too slow to stabilize a solid pellet. That twist rate, which is very often one turn in 16 inches of travel, was taken from the .22 long rifle cartridge when the first modern air rifle was made. It hasn’t changed since then. It works with diabolos, but not with solid pellets because they’re too heavy for the lower velocity at which most airguns can propel them. They have no additional means of stabilization and need to be driven faster to stabilize. Being both very heavy and also having a lot of friction with the bore, they go much slower in any given airgun.

Okay, make the airguns more powerful
About seven years ago, I could see where all of this was heading, so I tested these pellets extensively in an
AirForce Condor — the only air rifle I can afford that can get them up to 1,000 f.p.s. You know what? They still aren’t accurate. They’re stabilized at that speed, but they still shoot in 5-inch groups at 50 yards, while diabolos going less than 950 f.p.s. will group in three-quarters of an inch from the same gun.

Okay, then why don’t “they” make a more powerful air rifle that can shoot these things really fast?

Stop right there!
Don’t you see where this is heading? When an AirForce Condor shoots a 30-grain solid “pellet” at 1,000 f.p.s., it isn’t an air rifle anymore. It has become a firearm in all ways except how it’s powered. The Condor can shoot a 30-grain diabolo that leaves the muzzle at 1,000 f.p.s. and probably kill a woodchuck at 75 yards with ease, yet it still won’t travel downrange any farther than about 500-600 yards max. The high drag of the diabolo design slows the pellet after a very short time, but a solid pellet leaving the muzzle of the same gun at the same velocity will go a mile and a half. It has nothing to slow it down. We’ve then turned the Condor into a .22 short.

There’s an airgun maker in the Netherlands that makes custom .25-caliber rifles that can shoot 60-grain jacketed boattail spitzer bullets at over 1,200 f.p.s. That’s very admirable for an airgun, but that rifle, my friends, is a .25-20 Winchester in all ways but the name. Maybe not the modern loading of the cartridge, but it’s certainly close to the original loading. So, while it can actually be done, I’m saying that it shouldn’t be. Turning an air rifle into a firearm is just asking for more legislation that we don’t need.

Now, before some of you go off on big-bore airguns, they’re just as relatively safe as smallbore airguns. They shoot about as far as shotguns shooting rifled slugs, and most states that worry about distance limits for sporting guns allow the shotgun with slugs.

It’s not the power of the gun at the muzzle, but how far downrange it throws the projectile that makes it more or less safe. And, with diabolo pellets, airgunners have achieved something truly remarkable — a safer bullet.

I hope this report sheds some light on today’s state of airgun technology.

 

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