How Do CO2 Paintball Guns Work? The Complete Guide

Paintball guns are usually powered by air sources that help to cycle and propel the paintball. Carbon dioxide (C02) is a common propellant that has been used for several years and is usually stored in small cartridges or large tanks that are attached to the paintball marker. So how does a CO2 paintball gun work?

A CO2 paintball gun works in the following way: once cocked, the paintball falls from the hopper and enters the gun’s barrel. A small bust of CO2 is then released, pushing the paintball with great force, thus allowing for the paintball’s forward propulsion. This workflow is similar to a marker propelled by compressed air.

Curious to learn how CO2 paintball guns work? Then you couldn’t be in a better place. Read on as we compare the basic functionalities of CO2 paintball markers and their counterparts propelled by high-pressure air (HPA).

co2 paintball guns
The workflow of a CO2 paintball gun is fairly similar to the one filled with compressed air. The main difference is that CO2 is liquid in the tank and gets converted in the gaseous state when it comes out of the tank (you press the trigger).

The Main Parts of Paintball Gun: How It Works

Commonly known as a marker, a paintball gun comprises four main parts, the body, hopper, barrel, and air tank. These parts work together to ensure the gun functions as expected. Initially, compressed carbon dioxide (liquid form) was the most commonly used propellant. However, due to some disadvantages that we’ll discuss later on, high-pressure air (HPA) is preferred as a paintball gun propellant.

The hopper is an important component that carries paintballs, acting as a storage for ammunition and the gun’s loading mechanism. Hoppers are usually incorporated with firing assemblies that strategically maintain a single paintball in position until the trigger is pulled again.

While firing assemblies tend to vary depending on marker type, paintball guns usually function using the same mechanism. When you pull the trigger, the CO2 is then discharged through the airline in small bursts such that it enters the barrel. These guns work in a way that a paintball falls into the barrel (from the hopper) before the gas is released.

When the liquid CO2 exits the tank, the ambient heat within the gun helps convert the CO2 into a gaseous state, which then allows for the propulsion of the paintball.

CO2 (in the gas state) is then released behind the paintball. The high-pressure level of the gas pushes the paintball with great force from behind, such that the internal pressure exceeds the external pressure. The variance in pressure allows the paintball to propel forward with great force, thus allowing you to aim and hit a target.

Due to the risk of injury, you’ll find that the speed of most paintball markers is strictly regulated. On most occasions, paintball guns are regulated to manage a maximum speed of 300 feet per second, which translates to around 91m per second. You’ll need to be careful since, although the impact won’t cause serious injury, the balls can cause quite a sting, especially if they hit your bare skin.

Video: Co2 or Compressed Air, Which Ones Better?

The Advantages of Using C02 To Power Paintball Markers

 For paintballing purposes, CO2 is used in two vessel types, a 12- gram cartridge (paintball pistols and stock class markers) or refillable tanks. These vessels are usually filled with liquid carbon dioxide that expands to create enough pressure to propel the paintballs inside the barrel.

Although not as popular as before, CO2 markers come with a couple of advantages.

Besides being readily available, below are some of the main advantages of using CO2 as a propellant in your paintball marker.

  • Highly affordable and available: CO2 tanks are highly available, which reduces their overall costs compared to HPA. You don’t need to fill a CO2 tank in a paintball field since welding supplies and fire extinguisher shops can easily refill your tank. Here is a link to the article on the best places to refill your paintball tank.
  • More shots per fill: In a gas state, CO2 is denser than HPA, which translates to more shots and paintball propulsion per fill. This means you can do a lot more with a single CO2 tank than a similar-sized HPA tank.
  • CO2 tanks are affordable: It’s a lot easier to own a couple of CO2 tanks as they’re a lot cheaper than HPA tanks. This allows you to play more games, especially if you own more than three tanks.

Disadvantages of Using CO2 To Power Paintball Markers

  • Not compatible with all markers: Most modern paintball markers aren’t compatible with CO2. This is because CO2 is usually hard on a marker’s seals and can cause irreparable damage if it gets to the solenoids of most electro-pneumatic markers. There’s a couple of paintballing fields that no longer have the equipment to refill CO2 tanks.
  • CO2 cloud can obscure your vision: Unlike HPA, CO2 can obscure your vision due to the cloud that normally forms at the end of the barrel once the gun is fired. While you can still find a way to fire past the cloud, the CO2 cloud can end up giving away your position, especially when you’re playing with experienced paintballers.
  • Unstable pressure: The output pressure usually drops as the tank temperature drops. As a result, your overall velocity can drop significantly until you allow the tank to warm up again. Similarly, when the tank temperature gets too hot, it may over-pressurize and, therefore, lead to a spike in velocity, which might lead to injury.
  • Freezing: Did you know that CO2 expansion from liquid form to gaseous state more often than not chills the gun and the tank? Therefore, the more you shoot, the colder the entire system gets, thus increasing the gun malfunctioning chances, especially when playing in cold weather.  
  • Difficult to measure: You won’t get to know how much CO2 is remaining in the tank unless you remove the tank and place it on a weighing scale. This can lead to in-game disappointments, especially if you only have one CO2 tank.

The Advantages of Using HPA To Power Paintball Markers

Also called compressed air tanks, HPA tanks are filled with compressed air, similar to scuba tanks. These tanks are made from carbon wrapped aluminum or aluminum and can hold 3000-4500 psi in terms of internal pressure.

HPA tanks usually have valves that come with inbuilt regulators. These valves and the regulators help to lower tank pressure to a usable, game-friendly pressure. This leads to a standard output pressure of 850psi. However, depending on the installed regulator, the pressure can be adjusted such that it ranges from 300psi to 1100 psi, thus making the tanks suitable for a game of paintball.

HPA tanks were brought to the fold to counter the various temperature and pressure-related drawbacks associated with CO2 tanks. When using HPA tanks, it’s possible to shoot the gun as frequently as possible without having a shootdown, as would be the case with CO2 tanks.

Below are some of the advantages of using HPA tanks to power paintball guns. 

  • Consistent output pressure: One of the main advantages of HPA paintball tanks is their stable output pressure. The output pressure of HPA tanks is never affected by the external pressure, making HPA a great option for all-weather paintballing.
  • Doesn’t emit a vision-obscuring cloud: Unlike CO2, HPA doesn’t produce a cloud of gas that can obscure your vision during a game. While a cloud can be formed when playing in extremely humid conditions, the chances of obstruction are very minimal.
  • Compatible with all paintball markers: Since CO2 is gradually being phased out, you’ll find that most paintball markers are designed for HPA usage. Almost all paintball markers are HPA compatible.
  • Many paintball fields have unlimited HPA refills: The cost of refilling is usually charged per tank when dealing with CO2 tanks. However, with HPA, most fields charge flat fees of approximately $5-$10 to refill the tanks the entire day.
  • Easy refill: HPA tanks are among the easiest to refill. All you’ll need to do is attach the fill hose to the nipple and fill the gas. You won’t need to dump air inside the tank for a refill.
  • Adjustable output pressure: Some companies produce adjustable tank regulators that allow you to adjust the output pressure to your preferred level, provided it’s within the acceptable range.

The Disadvantages of Using HPA To Power Paintball Markers

  • HPA tanks are fairly costly: Compared to CO2 tanks, HPA tanks are significantly costlier, thus making it hard to purchase several tanks. The costs of HPA tanks can be as high as $250, depending on the material used in production and the installed regulator. And that is one of the reasons why paintball is quite expensive to play.
  • HPA tanks are bulky: HPA tanks are bulkier than their CO2 counterparts, making them a bit difficult to carry around. Despite their slightly larger sizes, the tanks don’t manage more shots per tank.

This might make you wonder if you can fill the CO2 tank with compressed air, after all the tank is cheaper? You can find out that and more in this article.

The Main Types of Paintball Guns

There are 3 main paintball gun types in paintball.

Pump Paintball Markers

Pump guns are the pioneers of paintball markers. Despite being basic in design and requiring manual operation, these guns have re-emerged in the market due to their ability to improve a player’s field skills and gun operation.

When using pump guns, you’ll need to pump it like a shotgun and chamber a paintball whenever you want to take a shot. Some pump guns like the Empire Paintball Sniper Pump Marker are extremely reliable and allow players to work on their shooting accuracy and field skills.

Point to note, though, first-time paintball players might struggle to use pump paintball markers, especially when competing with opponents using semi-automatic guns. But you’ll love using these guns if you fancy a shotgun approach.

Mechanical Paintball Guns  

As arguably the most common types of paintball markers, you’re likely to spot these guns in most (if not all) paintball fields. These markers are semi-automatic, inexpensive, and fairly easy to maintain. With the right set of accessories, mechanical paintball markers are easy to use and won’t take much getting used to.

Mechanical paintball guns stand out due to their versatility, as they can operate on both CO2 and compressed air. You can easily get your tanks refilled if you’re playing on a commercial paintball field or if you’re close to a pro-shop.

A large number of mechanical paintball markers use a unique blowback mechanism. The blowback mechanism kick starts a chain of internal activities that allow the barrel to fire the paintball. Basically, once you pull the trigger, it moves an internal sear catch that in turn releases a hammer or striker that’s under spring tension.

The hammer then hits the valve and opens it long enough to allow for the paintball’s propulsion from the barrel. The pressure released during the fire also throws the hammer back until it’s firmly caught by the sear. It allows for the process to repeat once another paintball lands in the breech.  

Generally, blowback markers usually come in two main designs: a stack tube design and an inline design. If you’re looking for a gas efficient mechanical paintball marker, you might want to go for the stack tube design. Inline markers make great options if you want a gun, you can upgrade later on to improve your overall game performance.

You can get the whole package kit including the highly-rated mechanical paintball gun (which in my opinion is the best mechanical paintball gun) on Amazon (showcase below).

Electronic Paintball Guns  

Although initially expensive, electronic paintball guns have become more affordable over the years. These paintball markers are usually powered by a 9-volt battery, which helps to power the electronic solenoid responsible for releasing fire.

With electronic paintball guns, players can achieve high rates of fire courtesy of an internal micro-switch. Pulling an electric paintball gun’s trigger is fairly easy, making it a great option for beginners. These guns have a circuit board that controls all commands that go to the solenoid, thus allowing the markers to manage various firing modes, including ramping, full auto, and burst.

Electronic paintball guns can be classified into three main types, the pneumatic poppet valve, spool valve, and the electric sear tripper.

  • The pneumatic poppet valves function similarly to stack tube blowbacks, the only difference is their usage of a pressure-powered ram instead of a striker. The pressure powered ram translates to gas- efficient, highly consistent, and very fast firing. Please note that pneumatic poppet valve guns only function with HPA. Using CO2 will almost certainly damage the solenoid permanently.
  • On the other hand, electric sear trippers are typically mechanically markers that rely on an electronic solenoid to activate the sear catch. Besides increasing the fire rate, this type of electric marker allows you to fire in several modes.
  • Spool valve markers are popular due to their considerably low maintenance. Since the only moving part is the bolt, they don’t have any recoil, allowing for increasingly accurate shots. They also shoot quietly and have a low compact profile, allowing you to move stealthily. The main disadvantage is their gas inefficiency. Be prepared to recharge your tanks a couple of times if you opt to go to friendly war with this highly capable marker.

Here is a link to the best automatic paintball guns article.

Main Parts of a Paintball Marker You Should Know About


Hoppers are holding and loading mechanisms of paintball guns. The type of hopper you have plays an integral role in determining the marker’s firing rate. There are four main types of markers, as discussed below.

  • Stick feds: This type of hopper is pretty much the most basic out there. It is highly affordable and only compatible with a pump marker due to its slow loading capability. A stick fed hopper can comfortably hold 10-20 paintballs and isn’t ideal for professional or even competitive recreational paintball.
  • Gravity-fed: As suggested by the name, this hopper feeds paintballs into the barrel through gravity. This gravity feed hopper isn’t much of an upgrade and is highly susceptible to jamming and sticking.
  • Agitating hoppers: This type of hopper is battery powered and features an agitator at the top to help prevent jamming or sticking. Agitating hoppers work best when used on mechanical markers.
  • Force-fed: Commonly used by professional paintballers, the force-fed hopper works best for electronic paintball markers. It works by forcing paints into the marker at impressive rates to suit the functionality of paintball markers.
Video: Gravity-Fed vs. Electronic Hoppers


The barrel is an important part of a paintball marker as it allows for the propulsion of the paints once they leave the hopper. Barrel length tends to vary depending on the type of marker used. 

The average barrel length for paintball markers, however, is between 3-21 inches. A short barrel will allow for increased speed and accuracy, while a long one will help suppress sound.


The body of a paintball marker contains various parts (depending on the type). However, the most common parts that you should know about include the cocking knob, trigger, and firing chamber.

The cocking knob helps to get the marker ready for firing a paintball. The firing chamber is connected to the hopper, which ensures it receives the balls once dropped down. It holds the balls before they’re released from the barrel.

The trigger kickstarts the firing process. Please note that the trigger release technique is important, especially when dealing with mechanical and electronic paintball markers. You should first understand the firing mechanism of a paintball marker lest you fail to pull the trigger in time and effectively.

Wrapping Up

Paintball guns need gas to propel the balls from the barrel towards the target’s direction. While CO2-powered paintball markers were initially popular, most modern paintball markers are designed to be compatible with high-pressure air.

CO2 tanks are easily affected by changes in temperature, which in turn compromises a player’s performance. As a result, HPA powered markers are more popular in paintball fields. Most mechanical and electronic guns use compressed air. However, if you’re keen on using CO2 to propel your paintballs, then it’s best to settle for a pump paintball gun.