Jaeger Precision goes over the Tapp Airsoft Hybrid HPA MP9 Lower conversion kit, which converts the KWA MP9 gas blowback SMG to use High-Pressure Air (HPA) and compatible ARP9-style magazines. He states his preference for the shorter, 70-round G&G quad-stack magazines to maintain the SMG's ergonomics. The initial and most intricate part of the video is a comprehensive walkthrough of completely disassembling the original MP9's lower receiver and meticulously transferring all the fire control unit components into the new 3D-printed hybrid lower.

A substantial follow-up is included to address functional issues, such as the gun "running away" on semi-auto, and a physical breakage on the first unit received. After Tapp Airsoft provided a replacement lower, the MP9 was able to function correctly, cycling reliably on full-auto at 100 PSI and demonstrating the benefit of sustained fire without gas cooldown. Although the replacement unit had a noticeably loose folding stock, the kit is ultimately recommended for players seeking the higher performance and capacity of an HPA system, despite the challenging and time-consuming nature of the assembly process.