The KWA/KSC/ASG MP9 GBB can be enhanced with the Airtac MP9 Shot Shell HPA Adapter, allowing users to switch to HPA as a power source. Jaeger Precision acquired one of these adapters for testing. The manufacturer claims 1J of energy at 100 PSI using 0.25g BBs can be achieved. This means heavier BBs or higher PSI can easily push the performance beyond UK field limits, bringing it closer to DMR territory (up to 130 PSI is possible with this adapter). The adapter functions reliably even at lower pressures, down to 80 PSI.

A key feature of this adapter is its CNC Valve Collar, which replaces the plastic thread valve for increased durability. It comes standard with a US HPA fitting, but EU push fittings are also available. To install the adapter, users need to rack their gun before insertion and provide a donor magazine. The donor magazine requires the removal of the gas valve, feed lips, gas router, and valve knocker, which are then transferred to the adapter. Airtac pressure tests each adapter before shipping to ensure compatibility and proper sealing with the user's RIF.

The Airtac MP9 Shot Shell HPA Adapter offers various configuration options. The modular adapter top can be purchased separately, allowing users to utilize existing modular bases. The adapter is compatible with different magazine types: M4 (best with PTS EPM1), MP5 (all CYMA MP5 Mid Cap Magazines), shotgun shell (CYMA and some other brands), and drum (Tokyo Marui MP5 or VZ61, or Well/Jing Gong). Modular mag-wells are also sold separately, providing flexibility for different setups and field restrictions.