Simple enough question, no? Maybe you get some confusion from certain air-powered tools or perhaps a slang reference to a paint sprayer, but most folks know exactly what you mean when you say airgun. Right? Think again.
The term airgun isn't found in most dictionaries yet. You'll find that your spell checker suggests writing it as two words, but that's not what this is about. I really want to know if you know what's meant by the term airgun.
At this point, some of you will stop and formulate an official-sounding definition that goes something like this. An airgun is any smoothbore or rifled gun that propels a projectile by means of compressed air. As you stand back to admire your work, it'll suddenly dawn on you that your definition doesn't encompass any of the guns that are powered by CO2. And you know there are a ton of those! Don't you hate it when that happens?
Well, don't stretch your brain any further, pilgrim, because you've just scratched the surface of this conundrum. Airguns, it turns out, can be a great many different things, and air is only one of the defining characteristics.
Before we move on, however, let's deal with the CO2 issue. Clearly, carbon dioxide isn't air. If you doubt it, try breathing it for a few minutes and then we'll talk. I've had arguments with airgun collectors who were stubbornly opposed to labeling CO2 guns as airguns. Now, while that's a fun subject for two people to banter, it doesn't serve a person who is drafting state legislation regarding new hunting laws in any way.
So, are CO2 guns airguns or not? Well, let's see. They're sold by airgun dealers, they travel under the same restrictions as guns that do operate on air, they use the same ammunition and they perform similarly. And heck, there are even a few amphibious models like Benjamin's Discovery that operate on either compressed air or CO2. Robert Kennedy was the one who observed that if something quacks like a duck, it probably is a duck. So, yes, is the answer. Guns that use CO2 are also airguns.
Green gas/red gas
Wouldn't it be nice if it ended there? Well, it doesn't. There are other propellant gasses that power guns that must also be considered, now that the door has been opened for CO2. I'm talking about green gas and red gas. The airsoft industry hates to admit it publicly, but green gas is actually propane. A tiny bit of silicone oil is added to the gas to lubricate the gun's parts as it functions.
They will even sell you adapters to fill your green gas guns from five-pound propane tanks, all the while backpedaling on admitting that green gas is propane!
Here's where it becomes interesting. Green gas develops a pressure of around 115 PSI at room temperature. That's plenty of push to propel a three-grain plastic ball (they call them BBs) out the spout at a fairly good clip.
Now, red gas is more exotic. It has a higher vapor pressure than green gas and requires some modifications in the guns that use it. If you read all the warnings, you'll get the idea that red gas is like nuclear fuel — but for one thing. Some airsoft guns also operate on CO2, which has a vapor pressure of 853 PSI at room temperature, which goes way beyond the pressure of red gas. To operate on CO2, airsoft guns have to be modified even more, and this is done by restricting the gas flow through special valving that has very small gas ports. So, there you are. Guns that run on green gas, red gas and CO2, none of which are air, fall into the airgun category, because there's no other category for them.
Airsoft guns do receive special legislation of their own because many are built to simulate firearms (called "real guns" by some folks), and they're used in force-on-force skirmishes with people shooting at each other. There are legal issues concerning brandishing in public and special markings on the guns that are not as applicable to the kind of pellet guns I generally write about, but they are also sold by the same dealers and often made by companies who make conventional airguns as well. Once again, they quack like ducks.
We're not finished with the non-air powerplants, yet. There are still catapult guns to consider.
Catapult guns propel projectiles by means of a spring in the form of an elastic band or even a conventional coiled steel spring. If you think CO2 guns cause controversy among anal airgun collectors, try raising this subject and see what happens.
The most common catapult guns are the Sharpshooter-series guns dating from 1923 and produced in the U.S. through at least the 1980s as toy novelties. These guns all shot .118 lead shot, which is more commonly known as No. 6 birdshot.
In most airguns, the use of dropped shot can be a problem because of inconsistent size. The shot can easily get jammed in barrels when it's oversized, which is why we seldom see real BB-sized shot (shot size BB is nominally 0.180 inches in diameter) used in antique BB guns. It simply isn't regular enough. But catapult guns seldom use barrels. Most often they simply place the shot to be fired in a shaped seat to hold it during acceleration, then release it cleanly at the end of the acceleration phase.
The Johnson Indoor Target Gun shot conventional steel BBs from a submachine gun-looking plastic frame. It used tubular elastic bands, much like modern surgical tubing, to launch a 5.1-grain BB at 100-150 f.p.s., depending on the strength of the bands.
But Daisy made a catapult gun that used steel springs. Their model 179 is a Spittin' Image replica of a Colt single-action revolver. Instead of just flinging the BB with the force of the spring, the 179's spring pushed a paddle that actually hit the BB — like a croquet mallet smacks a ball — just pushed out the barrel (and this is one of the few catapult guns that really does have a smoothbore barrel). It was whacked out like a line drive off a baseball bat.
Rigid airgun collectors are really challenged by catapult guns because of the Daisy connection. They don't want to include them in the body of legitimate airguns; but with Daisy being such a key player, they usually cave.
That sets them up for a huge disappointment when they suddenly learn that, in the 1840s, there was another catapult gun that launched lead balls of approximately .43 caliber with sufficient force to kill small game. The Hodges catapult gun is a long gun with no barrel but with all the Victorian styling expected of a naval weapon made in the 1840s. The thought among advanced collectors is that it was a foraging gun made for naval vessels. Except for the few parts that absolutely had to be made of iron for durability, the rest of the gun is fashioned from bronze and English walnut.
The elastic bands were anchored at the forward end by two Roman soldiers figures cast in detailed bronze relief. I've seen two such guns — the one pictured here is in remarkable preservation, and the other has been restored to working order and shot by its owner, who reports velocities of about 450 f.p.s. with 122-grain swaged lead balls.
The next branch on the oddity tree deviates toward those guns that shoot BBs and shot by means of the power of an exploding toy cap. Wamo made a minimum of five different models, and new ones surface every couple of years. The most recent I've discovered shoots potato plugs.
If a toy cap can launch a BB, what's to prevent it from igniting a small charge of black powder? And who decides what's "a small charge?" There have been .22-caliber, .36-caliber and even .45-caliber rifles made by Rocky Mountain Arms Corporation in modern times that operate by means of exploding caps igniting black powder. If you go back 100 years, there were some made then as well. They're clearly firearms when they use black powder, but what about those using caps alone?
And, as long as we are talking about caps, what prevents someone from using percussion caps and even primers to propel pellets and BBs? Apparently nothing, because it's been done. Are these all airguns, as well?
Not the end!
As you now see, the question of what constitutes an airgun is far from clear. Once you accept any of these deviations, the rest will come streaming through the same loophole. For instance, is a gun that also launches an arrow then considered a bow? And if so, is it legal to use during bow season?
Airguns are not terribly complex, but they are also not simplistic. The definition of what constitutes an airgun has been ongoing for more than a century and there is no end in sight.