NorthEast Airsoft GBB Sten to MP5 HPA Adapter
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**COMING SOON - Updated 2026 edition with high quality CNC MP5 magwell.**
This HPA adapter turns the GBB STEN into a far more skirmishable weapon. Use in conjunction with straight or short CYMA MP5 magazines.
Requires feed lips from a donor GBB STEN magazine. Valves are all pre-fitted for your convenience.
Requires sanding down of a small notch inside the feed lips. Trivial, happy to do for you / demonstrate if required :)
Do not run high PSI with this adapter. Our adapter will not explode, your gun will! Keep it < 120psi
DO NOT EXCEED 150PSI WITH ANY AIRSOFT HPA ADAPTER.
ALWAYS USE AIR REGULATED BY A SECONDARY REGULATOR (EG AT200, WOLVERINE STORM, POLARSTAR MRS).
CHECK YOUR PSI BEFORE CONNECTING AIR TO A HPA ADAPTER.
NEVER CONNECT OUR EQUIPMENT TO PAINTBALL AIR TANKS OR CO2 TANKS.
NEVER CONNECT OUR EQUIPMENT TO A TIPPMAN STYLE HPA LINE
AIRTAC Adapters
Each of our adapters is designed to be low profile while reaching field limit FPS. We design and manufacture all of our products to the highest standard, and do not charge extra for ‘premium’ features. Where applicable this adapter features:- Lifetime Warranty (Our adapters have to be built to last)
- Injection moulded or CNC magwell that is impervious to BB strikes at point blank skirmish FPS.
- CNC or Injection moulded Feed Tubes and Magazine Catches for lifelong durability.
- Tuneability/compatability via integrated shim systems. Our adapters are designed to cope with 'airsoft tolerances'
- Gas Routers injection moulded from NBR, 1:1 with the factory gas router.
- Seal Test
- Firing test, for feed and recoil (we have over 100 guns on site for testing)
MP5 HPA Adapter Info
- This magwell is made of CNC aluminium and cannot be damaged by BB strikes.
- Compatible with all CYMA MP5 Mid Caps (65 round metal, 120/130 round metal, Straight, Novritsch Straight, Bullet Window). Available Here
- BB Retention drops only 2 BBs when changing magazine
The feed tube shim fits under the feed tube. The rear shim is held in by two screws.
- Straight Magazines (Default Config) - Keep Shim In. Feed Tube spacer necessary on newer CYMA MP5 magazines
- Curved Long / Short Magazines - Remove rear shim. Keep Feed tube spacer in.
- If straight magazines will not feed with the rear shim and feed tube spacer installed, try removing the rear shim.
- In the very rare case short CYMA magazines do not fit your adapter, contact support@AIRTAC.me (we can solve this for you ASAP)
Compact MP5
Key Information
- We use a US Foster Fitting as standard. This is the most common airsoft HPA fitting. EU fittings can be purchased separately.
- Some of our HPA adapters have a smaller internal volume than gas magazines. Because of this, you will need to use a PSI of 90–150.
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If you need higher FPS, you can:
- Fit a tighter barrel
- Use a longer barrel
- Use heavier BBs
- Fit an improved hop bucking
- If your replica has an NPAS fitted, we advise opening it fully.
- Do not exceed 150 PSI. Many airsoft guns will not see an increase in FPS past this, as the hammer may struggle to depress the valve correctly.
- Insert the HPA adapter with your bolt / slide locked back to minimise pressure against the nozzle loading arm.
DO NOT EXCEED 150PSI WITH ANY AIRSOFT HPA ADAPTER.
ALWAYS USE AIR REGULATED BY A SECONDARY REGULATOR (EG AT200, WOLVERINE STORM, POLARSTAR MRS).
CHECK YOUR PSI BEFORE CONNECTING AIR TO A HPA ADAPTER.
NEVER CONNECT OUR EQUIPMENT TO PAINTBALL AIR TANKS OR CO2 TANKS.
NEVER CONNECT OUR EQUIPMENT TO A TIPPMAN STYLE HPA LINE