Call me naive or even stupid... But I really don't see what all this bipolar hype is all about?
Running a line from the gun to the tank just seems like a backwards step for me?
While we are at it, let's start building steam powered cars, thatched roofs and candle based illumination systems. I know what, let's take a step backwards and then pay extra for the priviledge of doing so! Hi five mofos
HPA has actually advanced a fair bit.
the first HPA airsoft guns were fully mechanical,using cam mechanism to move around nozzle and valves,and such. This is just a big simplification btw. Most of the parts were made of cast brass,had LOTS of springs and little fiddly parts.
Modern HPA guns,like the Kuba engine,Polarstar fusion engine and other use electrical parts like solenoids and computerized triggers. This allows a greater deal of efficiency and reliability due to less moving parts. If the solenoid/trigger is programmed correctly HPA will always come out at the exact same volume,miles more consistant than a traditional AEG or GBB. Mechanical designs are also about,akin to something out of a GBB.
HPA is more expensive because you need a tank and air line,they solenoids they use are also pricey. Polarstars are pricey because everything in CNC milled out of billet aluminium on a low volume production. In comparison a reliable Chinese AEG gearbox costs as little as 20 pounds.
The cheapest HPA system is a Kuba system- It's essentially a solenoid,valve and cylinder. You can build one yourself if you have a mill for as little as 80 pounds including a simple trigger boards. The design is fully open source and you can get blueprints for free.
The price of a Kuba system made out of 6061 aluminium or so is cheaper than a Lonex drop in gearbox which commonly goes for 90-100 pounds. It;s roughly the same price of a well built gearbox with a mix of SHS and Lonex parts. but,you get far far better reliability and consistency.
The base line is that modern HPA powered guns are more reliable,simpler and consistant than an AEG. My knowledge on HPA is only from adventures in the 705th Chairborne ranger division,not near as much as I know about VSRs or AEGs.