Easiest HPA Systems To Install

Easiest HPA Systems to Install

Airsoft can be a very competitive sport, and players are always trying to gain an edge over their opponents. HPA or high-pressure air systems improve the performance of airsoft guns and are a definite advantage when in the field.

In this article, we’ll show which HPA systems are available on the market and which of them are the easiest to install. We’ll also provide a basic installation guide along with some tips on using the HPA system.

What Is HPA, and How Does It Compare to GBB and AEG?

HPA, as the name suggests, uses highly pressurized air to fire ammunition out of an airsoft gun. It’s similar to GBBs or Gas Blowbacks except for the actual gas used as fuel. HPAs are superior to GBBs in performance as temperature changes don’t affect pressurized air; meanwhile, GBBs usually operate worse when colder.

AEGs or automatic electric guns usually have lower FPS than HPAs as voltage limits the speed of an AEGs launch mechanism. Most AEGs come at seven to nine volts by default, and it takes a highly modified internal system to withstand an 11-volt battery. The speed of an HPA system can be adjusted via the air canister and needs minimum adjustments in the gun’s internal system once it’s been set up.

What Are the Easiest HPA Systems to Install?

Below are some of the more popular HPA systems in the market and what they offer to the airsoft enthusiast.


Polarstar HPA

Polarstar is a very popular brand when it comes to HPA systems, and they provide several models with varying levels of complexity. Conversion kits require you to gut the gearbox to install the HPA module, while drop-in kits replace the entire gearbox.

Here’s a list of their models:

Polarstar Jack: Many consider the Jack a good introduction to HPA systems, as it’s one of the most basic HPA in the Polarstar line. Since it’s a drop-in kit, it’s relatively easy to install, and with only the nozzle as a moving part, maintenance is also simple. There are several versions available intended to fit several types of gearbox frames.

Polarstar F1: The Polarstar F1 is a conversion kit, meaning that you’ll need to remove the contents of the gearbox to install it. Setup is rather straightforward, however, and can be done with minimal technical experience. This kit has an FCU or fire control unit; thus, it requires a battery to operate.

Polarstar F2: Another cylinder drop-in kit, the F2, is an improved version of the previous HPA system and uses a dual solenoid design. As with other conversion kits, installation is easy as you only need to remove the gearbox’s internals.

Polarstar Fusion Engine: As a full gearbox replacement kit, the Fusion Engine is simpler to install than a conversion kit. The only real downside is that it’s relatively more expensive than the other Polarstar HPA models. The Fusion Engine is highly customizable and comes with several variations to fit M4s, AKs, and MGs. The kit also requires an FCU, so a battery is needed to operate.

Polarstar Kythera: Polarstar’s latest model, the Kythera, is a drop-in conversion kit, so installation requires opening up your current gearbox. Actual performance hasn’t been reviewed yet as the product is currently on pre-order.



The Redline HPA system brand is a favorite among MilSim modders as the closed bolt systems offer better accuracy and more consistent velocities. Some of its most recommended models are as follows:

Redline SR-E Lightning: As a closed bolt drop-in HPA conversion kit, it requires the modder to empty the gearbox like other conversion kits. Setup should be straightforward and shouldn’t deviate too much from how other HPAs are installed. Unlike other models from Redline, the SR-E Lightning can fire on full auto, although most fields ban full auto during play. This kit also requires an FCU, so a battery is needed for operation.

Redline SR-M Hurricane: Another closed bolt HPA system, this cylinder replacement kit installs similarly to the SR-E Lightning. This model fires in semi-auto mode only, though this doesn’t need an FCU to operate; thus, no batteries are required.


Wolverine HPA

Another very popular brand, Wolverine, offers top-of-the-line products, though some models are more complicated to assemble than others. Wolverine has an extensive lineup of a variety of airsoft guns.

Some of the most recommended models are:

Wolverine BOLT: One of the few HPA systems available for sniper rifles, the BOLT requires a battery, though it doesn’t use an FCU. When converting previous spring rifles to this HPA system, the cylinder might be incompatible, so buying a separate cylinder is recommended. Unlike standard drop-in HPA systems, the BOLT may require a Dremel tool to fit the HPA engine properly. In addition, depending on the type of rifle you have, additional drilling may be necessary to install the air hose.

Wolverine Reaper: The Reaper is a closed bolt drop-in cylinder replacement kit designed to replace the firing mechanisms of AEG rifles. Simpler to install than the BOLT, it still requires taking the gearbox apart. This model also requires a battery for the FCU.

Wolverine Gen2 Inferno: Wolverine’s top-of-the-line HPA system, the Gen2 Inferno, can fit most gearbox models without additional modifications. Many consider the Inferno’s performance similar to Polarstar’s F2 and is a great alternative to the model. It can fire on semi-auto and full-auto and uses an FCU, thus requiring batteries to operate.


Daytona HPA is on the more expensive side

One of the more expensive HPA kits out there, Daytona, is what you get if you want the realistic recoil of a gas blowback system with the performance of an HPA. Most of Daytona’s HPA models are created to fit specific gun types and require more technical skill to install on your own. As Daytona assemblies feature moving parts, it’s recommended that AEG barrels be made out of steel or brass, as aluminum will bend during use. Daytona HPAs are recommended for advanced users.

The Most Beginner Friendly Kit

Considering all the kits presented above, the easiest HPA system for beginners would be the Polarstar Fusion Engine. Many of Polarstar’s products are very simple to install, but the Fusion Engine as a full gearbox replacement is the most straightforward. Users don’t need to tinker with the triggering mechanisms or remember tubing placement. Just remove the entirety of your old gearbox, then replace it with the HPA kit.

Steps to Install a Drop-In HPA

If you want a more versatile HPA system, you might want to try a drop-in kit instead of a gearbox replacement. Although not all HPAs are created equal, most drop-in conversion kits are made similar to each other as they need to fit the standard gearbox. The following are the usual steps required when converting an AEG rifle into an HPA system.

1.      Take out the gearbox from the gun.

Remove the screws holding the two halves of the gun together on the outside of your AEG. Inside, you should find a container with wiring running out of it. This is the gearbox. Remove any screws holding the gearbox in place, if any, then pull it out from the gun’s body.

2.      Open the gearbox.

Remove the screws that are holding the gearbox closed. Remember to separate these screws from the ones used for the cover of the gun.

3.      Remove everything inside the gearbox.

You’ll only need the gearbox casing itself for a drop-in HPA. The spring, gears, and piston won’t be necessary, so take them out. You will need to keep the trigger, and the buffer tube, so set them aside for later.

4.      Install the trigger board.

Your HPA system should come with a trigger board. It will look like a small circuit board, and it controls the output of the HPA system. Place the board where your original trigger mechanism was located. Screw the board in place.

5.      Place the HPA module in the gearbox.

The module should be placed where the piston was originally in the gearbox. Make sure that it's appropriately aligned before proceeding.

6.      Connect the module to the trigger board.

Refer to the manual of your HPA system to locate which wire connects to the trigger board. The wire should click onto the board.

7.      Connect the wiring harness.

Your HPA system should come with another wire that slots onto the trigger board. If your model doesn’t have one, your particular HPA might not need an FCU. In that case, skip this step.

8.      Position the air tube and wiring harness.

The air tube should normally bend down in the direction of the grip, but if you plan to run the tubing onto the gun’s stock, adjust the position of the air tube as required.

9.      Put the trigger back in.

Place the trigger in the same place where you removed it. Give the trigger a few pulls to see if it's properly aligned.

10.  Put the buffer tube back in.

The tube should face the HPA unit.

11.  Close the gearbox.

Make sure that all the proper screws are replaced to their original positions.

12.  Install the gearbox back onto the gun.

Pros and Cons of Using an HPA

So now that you’ve familiarized yourself with the HPA system, you should consider the pros and cons of getting one yourself. Here are some quick advantages and disadvantages of an HPA.


Very Stable Performance

Each round fired does not lose speed compared to AEGs and Gas blowbacks. The constant FPS means that any adjustments made to the hop-up will stay consistent throughout the game’s entirety. If you want a gun that maintains accuracy for an extended period, then an HPA might be for you.

Quick FPS Adjustment

Adjusting the FPS on an HPA requires only turning the regulator on the air tank or the built-in regulators for models that use them. Note that some fields require tournament locks on HPA tanks to prevent adjustments while in-game. This is mainly used to keep players from cheating by exceeding maximum FPS limits.

Basic HPAs Have the Same Performance as High-Level AEGs

Even the most basic HPA systems can produce the performance quality of expensive AEG builds. Increasing the FPS on a battery-operated gun requires extensive modifications of the interior.

Silent Operation

Unlike AEGs and gas blowbacks, an HOA gun produces very little noise while firing. This is an advantage if you don’t want to give up your position when hiding from opponents. However, it’s a disadvantage if your objective is to provide suppressing fire for your teammates.

Suppressing fire usually requires that your opponents hear the loud bursts of your gun, so they keep their heads down and allow your team to move. If you’re sniping, however, this is a very big advantage.

Minimal Maintenance

HPA systems usually have very robust builds and require very little maintenance. As they don’t have too many moving parts, a quick clean-up now and then is all that’s needed to keep it in top shape.


Relatively Expensive

HPA systems present a steep upfront investment and require you to disassemble your current hardware. Even basic systems can cost the price of a new AEG. If you only play casually, getting an HPA system may not be worth the asking price.

Not Allowed on Some Fields

Because of the ease of adjusting the FPS, some fields don’t allow HPAs in their games. Although tournament locks alleviate this somewhat, some harmful stigmas remain about the system itself. Until proper regulation on FPS adjustment becomes standardized, expect a few fields to deny entry to HPA guns.

Tank Transport Can Be Inconvenient

As an HPA user, you’ll need to lug a tank along to play. This is fine for short games, but some MilSims can last for days, and bringing multiple tanks can become tiresome. Several backpacks alleviate this somewhat, and hydration packs have become a standard for multi-day events.

Air Hoses Can Get Stuck During Outdoor Play

Another disadvantage of an HPA gun is that your air hose can get stuck to branches or corners whether you’re playing indoors or outdoors. The only solution to this is to be aware of your surroundings and never turn too quickly unless you’re sure your air hose is safe.

HPA Safety Tips

If you’re using an HPA system, here are a few tips that you should keep in mind:

  1. Never put oil or grease on your tank’s fill valve. The tank does not require lubrication, and oil or grease can cause the tank to combust during refill.
  2. Hydro-test your tank every so often to check for leaks. Your tank should have a recommended date for hydro-testing.
  3. Store your tanks in a cool and secure place. When traveling, make sure that the tank doesn’t move around unnecessarily.
  4. Turn off the tank and allow the air to bleed out when not in use. This eases the pressure on the tank and increases its longevity.

Significant Performance Improvement

Although HPA systems are quite the investment, they can significantly improve the performance of your airsoft gun. Although not all HPAs are easy to set up, some systems only involve quick alterations to the gearbox. Hopefully, you’ll find this list of the easiest HPA Systems helpful to help you start on your modding journey.