PewClub Entertainment built a builtpup KCO2 airsoft rifle with the SRU kit... "This SRU bullpup kit for the ASG /KJ KCO2 thrilling your Si-Fi fantasy. Light weight and balance design ideal for CQB also perfect for woodland and outdoor. Powered by the Primary Airsoft HPA adapter makes it even more unstoppable."

PewClub Entertainment finds it fun using the Tokyo Marui MTR-16 GBB that uses HPA as power source with the AirTac HPA Adapter. This HPA adapter is a shortened magazine and HPA adapter for the Tokyo Marui GBB MWS from the ground up. The outcome is an extremely lightweight configuration that offers a more enjoyable and cost-effective alternative to purchasing gas magazines. It requires a donor magazine for the feed lips, exhaust valve, gas route, and valve knocker.