From Green Gas to HPA: The Ultimate Primary

Here's post 2 of 15 — the installation guide.

From Green Gas to HPA: The Ultimate Primary Airsoft Adapter Installation Guide

You've finally pulled the trigger. You have the HPA tank, the low-pressure regulator, the airline, and the box sitting on your workbench contains the key to limitless airsoft performance: a Primary Airsoft HPA adapter.

Whether you are converting a standard Hi-Capa, a G-Series, or an AAP-01, moving from standard green gas magazines to an HPA adapter can seem intimidating. If you are buying a pre-assembled adapter (where Primary Airsoft has already attached the polymer base to a donor magazine), your job is incredibly easy. But if you purchased the adapter base by itself to install onto your own existing gas magazine, you have some wrenching to do.

This guide will walk you through the complete installation process, from tearing down your old green gas magazine to tuning the HPA pressure for your first test shots.

Part 1: Pre-Assembled Adapters (The Plug-and-Play Method)

If you purchased a fully assembled adapter directly from Primary Airsoft or a retailer, it arrived already attached to a metal donor magazine body.

What you need:

  • Your pre-assembled adapter
  • An HPA tank (filled)
  • A Low-Pressure Regulator (LPR) and airline
  • An M4 or MP5 mid-cap magazine
  • High-quality BBs

Step 1: Connecting the Air

  1. Screw your Low-Pressure Regulator (LPR) onto your filled HPA tank. Ensure the regulator adjustment screw is backed out so the output pressure reads zero PSI.
  2. Connect one end of your airline to the regulator.
  3. Push the quick-disconnect collar back on the other end of the airline and snap it onto the Foster fitting at the bottom of your Primary Airsoft adapter. Pull on the hose slightly to ensure it is locked in place.

Step 2: Pressurizing the System

  1. Slowly turn the adjustment screw on your regulator clockwise.
  2. Watch the pressure gauge. Bring the pressure up to 80 PSI.
  3. Listen closely to the adapter. You should hear absolutely nothing. If you hear a hiss, check the Troubleshooting Guide for leak fixes. If it is silent, you are ready to load.

Step 3: Loading and Firing

  1. Use a speedloader to fill your M4 mid-cap magazine with premium, seamless BBs.
  2. Insert the M4 magazine into the bottom of the Primary Airsoft adapter. Give it a firm tap on the bottom to ensure the aluminum catch engages.
  3. Insert the entire adapter assembly into your pistol's magwell. It will click into place using the pistol's standard magazine release.
  4. Rack the slide on your pistol to load the first BB.
  5. Fire a test shot over a chronograph. Adjust the regulator pressure up (maximum 120 PSI) or down to meet your field's FPS limits.

Part 2: Installing an Adapter Base onto Your Own Magazine

If you purchased just the polymer adapter base to save money, you will need to sacrifice one of your existing green gas magazines to build the unit.

What you need:

  • A compatible green gas magazine (e.g., standard Hi-Capa 5.1 mag)
  • The Primary Airsoft adapter base kit (includes the base, the main screw, and the O-ring)
  • A set of small punches (or a small Allen key)
  • A Phillips head screwdriver
  • 100% pure silicone grease (not oil)

Step 1: De-gassing the Donor Magazine

CRITICAL SAFETY STEP: Never disassemble a pressurized gas magazine.
Press the exhaust valve button on the back of the magazine firmly to release any stored green gas. Ensure the magazine is completely empty.

Step 2: Removing the Baseplate

Most airsoft pistol magazines have a plastic baseplate that slides off the bottom, revealing the metal floorplate.

  1. Slide the plastic baseplate off.
  2. Look at the bottom of the metal magazine. You will see a large Phillips head screw in the center of the metal floorplate.
  3. Unscrew this Phillips screw completely.
  4. Pull the metal floorplate out of the bottom of the magazine. Note: Sometimes the floorplate is stuck tight. You can gently pry it out or tap the side of the magazine against a desk to dislodge it.

Step 3: Removing the Follower and Spring

  1. Once the floorplate is removed, the long magazine spring and the plastic BB follower will slide out of the bottom.
  2. Remove the spring and the follower. You won't need these parts for the HPA build, but keep them in your parts bin in case you ever want to convert the magazine back to gas.

Step 4: Prepping the O-Ring

Your Primary Airsoft kit includes a large, square/rectangular O-ring.

  1. Clean the lip at the bottom of your metal donor magazine where the floorplate used to sit. Ensure it is free of old grease and dirt.
  2. Apply a generous coating of 100% pure silicone grease to the new O-ring provided by Primary Airsoft.
  3. Carefully place the greased O-ring into the corresponding channel on the top of the polymer Primary Airsoft adapter base.

Step 5: Assembling the Unit

  1. Slide the polymer adapter base up into the bottom of the metal donor magazine. Make sure the feed tube in the adapter lines up with the BB channel in the metal magazine.
  2. Insert the long assembly screw (provided with the kit) up through the bottom of the adapter base and thread it into the metal donor magazine.
  3. Tighten carefully. Use a screwdriver to tighten the assembly screw until it is snug. Do not over-tighten. Over-tightening will crush the O-ring, squeeze it out the side, and cause a massive leak. You want it firm, but not cranked down.

Step 6: The Pressure Test

Now you need to test your assembly work.

  1. Connect your airline to the adapter.
  2. Slowly turn the pressure up on your regulator to 80 PSI.
  3. Listen for leaks at the seam where the metal magazine meets the polymer adapter.
  4. If you hear a hiss, tighten the assembly screw one-quarter turn and listen again. Repeat this quarter-turn process until the leak stops.

Part 3: Modifying Your Pistol for HPA

Installing the adapter is only half the battle. Because HPA delivers dry air at a highly consistent pressure, you should make a few minor modifications to your pistol to ensure longevity and performance.

1. Lubricate the Piston Head

As mentioned in our Maintenance Guide, HPA air is completely dry and will strip the factory grease off your pistol's internal O-rings. Before firing your new HPA setup, pull the slide back, pull the nozzle forward, and place two drops of lightweight silicone oil on the piston head O-ring inside the blowback housing.

2. Upgrade the Recoil Spring (Optional but Recommended)

Because HPA does not suffer from cool-down, your pistol will cycle much faster and harder than it did on green gas. To prevent the slide from slamming aggressively into the frame and cracking (especially on plastic-slide guns), install a stronger recoil spring. A 120% or 140% recoil spring will absorb the extra energy and snap the slide forward faster, improving your fire rate.

3. Upgrade the Nozzle Return Spring (Optional but Recommended)

If you are running a Hi-Capa or a G-Series on HPA, the fire rate can sometimes outpace the plastic loading nozzle. If the nozzle doesn't snap back fast enough, it will crush the next BB trying to enter the chamber. A 140% nozzle return spring ensures the nozzle gets out of the way instantly, preventing jams.

Conclusion: Ready for the Field

Installing a Primary Airsoft adapter is a rite of passage for competitive airsoft players. Once you have mated the adapter to your magazine, checked your seals, and dialed in your regulator pressure, you have essentially built a new class of weapon.

You no longer have to worry about the weather affecting your gas pressure. You no longer have to reload after every 25 to 30 shots. You simply plug in, load up an M4 magazine, and dominate the field.

If you haven't picked up your kit yet, or if you need to browse compatible M4 magazines, visit the Primary Airsoft Adapters.

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