Kross Airsoft Design Hi-Capa MP5 HPA Adapter

Hi-Capas are gloriously capable pistols and abysmally short of magazine capacity. A standard Hi-Capa mag holds 30 rounds; an MP5 mid-cap holds 100+. KAD's Hi-Capa MP5 HPA adapter bridges the two — running your Hi-Capa as an HPA platform fed from full-size MP5 magazines.

The adapter ships in two configurations. Adapter Only suits techs and tinkerers who'll source and fit their own donor mag. Fully Assembled comes pre-built around a donor magazine — recommended for anyone who hasn't done HPA mag work before, or who simply doesn't fancy spending an evening with pin punches.

CYMA metal mid-cap MP5 magazines are KAD's recommended donor for the cleanest feed. Other brands work but tolerances vary.

How HPA changes a Hi-Capa

Stock gas Hi-Capas are temperature-sensitive — green gas pressure drops in cold weather and the slide cycles unreliably below about 8°C. HPA converts the gun to run from a regulator at a fixed pressure year-round, so cycle rate, FPS, and trigger response stay constant from a July afternoon to a January frost. For UK skirmishers playing through autumn and winter, that's the whole reason to make the switch.