A look at the Begadi's very own HPA engine which can utilise CO2 as well in this review by REAPERs Airsoft... "Hello guys, today we're taking a look at the new Begadi HPA Engine. This is a mechanical, CNC manufactured and flexible engine which is available in many models."

There is another HPA enginer on the block and it is the SPECTRE HPA engine from Scalar Airsoft and the company shows how to assemble it in this video... "SPECTRE is a new, high performances electropneumatic HPA drop in engine kit. It replaces internal parts inside the gearbox shell of AEG replicas, with Tokyo Marui standard V2/V3 dimensions.

Tom Tong shows his 3D printed Airsoft HPA engine with 2 stage trigger and Arduino FCU prototype in this video... "My finished prototype! Now to design and print the sub machine gun shell to fit it in. Plans to add a shot / ammo counter that will count down to zero as the BBs are fed into the hop up chamber. More to come..."