Airguns 101 – the Basics: Powerplants

Monday, December 16, 2013

Go to virtually any fast food restaurant, and you can witness people creating and using airguns. No, I’m not kidding. Wait a little while, and you’ll see a kid tear one end off the paper wrapper on a soda straw, blow air through the straw, and launch the paper wrapper at someone. That’s an airgun, plain and simple. All airguns use the same principle – gas (air or CO2) moving down a tube – to launch a projectile.

There are a variety of powerplants that are used in modern airguns to get the air moving and send a pellet or a BB down range. There really is no such thing as a “perfect” airgun powerplant. All of them have advantages, and all of them have disadvantages. The one that will work best for you depends on which performance characteristics are top priorities for you.

In case you think airguns are a modern development, they’re not. Folks were experimenting with pneumatic airguns in the late 1500s, and by the 1700s, gentry were using them regularly for hunting. Lewis and Clark carried an air rifle with them on their historical journey of exploration of 1804-1806.

So let’s take a look at those powerplants.

Multi-stroke pneumatic

 

The 1377c is a classic multi-stroke pneumatic pistol.

The 1377c is a classic multi-stroke pneumatic pistol.

Multi-stroke pneumatic (also known as MSP or pump-up) airguns require multiple strokes (usually 2-8, but sometimes more) of an on-board lever (very often, the forestock) to store compressed air in the powerplant. The more you pump, the more air is stored and at higher pressure, which means the faster the pellet will be driven down range when the shot is triggered.

Advantages: MSPs are virtually recoilless, which means that they are easy to shoot well; you don’t have to worry about how you hold or rest the gun to get the best possible accuracy out of it. In addition, pump-up airguns are completely self-contained, so all you need for a day afield is the gun and a tin of pellets. In addition, the velocity of the pellet (and consequently the power with which it hits the target) can be varied with the number of strokes. Fewer strokes generally result in a quieter shot.

Disadvantages: The main downside of a multi-stroke pneumatic is that once it has been fired, it must be pumped up all over again. While some shooters find all that pumping very tedious, other liken it to shooting a blackpowder muzzle loader. Another consideration: when pumped up to the max, a multi-stroke pneumatic can be loud.

Single-stroke pneumatic

Single-stroke pneumatic airguns also use a lever to compress air in the powerplant, but – as the name implies – require only a single stroke to fully charge the gun. This is the powerplant that was used on many Olympic 10-meter match guns and is still used on some entry-level match rifles as well as some air pistols.

Advantages: Single stroke pneumatics are fully self-contained, easy to cock, highly consistent and often incredibly accurate.

Disadvantages: There is a limit to how much air you can compress in a single stroke. As a result, the power and speed of these guns is usually low, shooting relatively light match-grade .177 pellets at 500-600 fps.

Precharged Pneumatic

The Cricket is a pre-charged pneumatic rifle in a bullpup configuration.

The Cricket is a pre-charged pneumatic rifle in a bullpup configuration.

Precharged pneumatic airguns are similar to similar to single and multi-stroke pneumatics in that the shot is driven by compressed air stored in a reservoir on the rifle or pistol. But precharged pneumatics (also known as PCP guns) are charged not from an on-board pump, but with air from a SCUBA tank or high-pressure pump. This is powerplant of choice for high-energy hunting guns, Olympic 10-meter rifles and pistols, and top-echelon field target rifles.

Advantages: Pre-charged pneumatics are virtually recoil-free, very consistent, and typically superbly accurate. They can also been extremely powerful. (This powerplant has been used to create big bore air rifles used for hunting large game.) In addition, some manufacturers have broken the “high-price barrier” with the introduction of PCP rifles that cost roughly as much as a magnum spring-piston rifle.

Disadvantages: Until recently, precharged airguns have been generally expensive. In addition, they are not self-contained – you need a SCUBA tank or high-pressure hand pump available to recharge the gun – as a result, they are sometimes viewed somewhat complicated to operate.

Spring-Piston/Gas Ram

The Weihrauch HW80 is a fine example of a breakbarrel spring-piston air rifle.

The Weihrauch HW80 is a fine example of a breakbarrel spring-piston air rifle.

Spring-piston airguns – also called “springers” – use a lever (normally the barrel or a lever under or to the side of the barrel) to cock a spring and piston (or a gas cylinder “gas spring” in the case of a gas-ram powerplant). When the trigger is pulled, the spring (or ram) is released, pushing the piston forward (and the gun backward) and compressing a powerful blast of air behind the pellet. As the piston nears the end of its stroke, it slams into the wall of air at the end of the compression cylinder and recoils in the opposite direction. All this happens before the pellet leaves the barrel. (In effect, the springer creates a short blast of compressed air on demand.) The recoil effect is the same for a gas ram.

Advantages: Springers are a favorite of many airgunners because they are self-contained, often relatively quiet and can be very accurate.

Disadvantages: The Dark Side of springers is that, because their unique whiplash recoil, these guns often require considerable practice to shoot them at their highest accuracy. In addition, the unique recoil of springers demands airgun-rated scopes that can withstand the forward-and-back recoil.

CO2

The Walther Lever Action is a CO2 powered repeater rifle.

The Walther Lever Action is a CO2 powered repeater rifle.

CO2 airguns are powered by 12-gram cartridges, 88-gram AirSource cartridges, paintball tanks, or CO2 transferred from a bulk tank into the gun’s on-board reservoir. These cartridges and tanks actually contain CO2 liquid some of which vaporizes in the tank at very low temperatures, producing a high-pressure gas which is then used to propel pellets or BBs down the barrel. The gas pressure produced when the liquid vaporizes depends on the ambient temperature: the lower the temperature, the lower the gas pressure, and therefore the lower the velocity of the pellets.

Advantages: CO2 airguns are recoilless, and (in high quality models) extremely accurate. They are also very convenient; it’s easy to carry a handful of 12-gram cartridges in a jacket pocket. The convenience of the cartridges has also made CO2 a popular propellant for air pistols. Noise levels vary from model to model. Cocking effort is usually very low, making these guns a favorite for family shooting.

Disadvantages: CO2 airguns require periodic refilling and performance will vary with temperature. Velocity will drop considerably in wintry conditions, and CO2 airguns will shoot faster than normal in very warm conditions. In addition, CO2 airguns should not be stored in temperatures above 120 degrees F.

What’s the Best Choice?

So which airgun powerplant is right for you? If you want a gun that is self-contained, choose a spring gun, multi-stroke pneumatic, or single-stroke pneumatic. If you want a neighbor-friendly report, a spring powerplant is most likely to deliver it, and there are quiet pre-charged, multi-stroke, and CO2 models. If you demand the highest accuracy, a single-stroke pneumatic match rifle or a precharged gun is the way to go. Usually the shortest range airguns will be the single-stroke pneumatics, while some of the precharged rifles are suitable for varminting at rimfire distances.

There is no single powerplant type that will satisfy every requirement. This accounts for why so many airgun enthusiasts acquire several airguns and enjoy the unique advantages of each one.

Til next time, aim true and shoot straight.

–          Jock Elliott

6 Comments

  1. Steven G says:

    Jock, I am in the springer camp. Mainly they are “Tough”. They are self contained. A really tough pcp
    would work for me but I haven’t seen one yet. I found out that the rear stock on a benji is held on but one piece…I guess I need to just stay with throwing rocks.
    I like the new 101 idea,I will keep reading! Thanks

    1. Jock Elliott says:

      Steven G,

      Thanks for the kind words and the comments.

  2. Duncan McPhee says:

    Hey Jock. Just want to say thank you very much. I am about to buy my 3rd air rifle and couldn’t decide what to buy. The lack of detailed articles on the web amazed me but so glad I found you here, now all of my questions have been answered. Cheers buddy and thanks again. Keep up the good work mate. Duncan

    1. Jock Elliott says:

      Duncan,

      Thank you so much for the kind words. I’m glad the articles are proving useful.

  3. Chris says:

    I just bought my first air rifle. No one at three big sporting stores in town could tell me the difference between nitro and spring power plant. I just found your web site and wanted to thank you for clearly explaining the various power plants. Thanks again.

    1. Jock Elliott says:

      Chris,

      Thanks for the kind words. I’m glad the blog proved useful.

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