HPA airsoft is becoming big in Russia, especially with their colder climate, players prefer a more consistent source of power as gas blowbacks are usually ineffective, and batteries also run out of juice quicker. With HPA, they have a stable power source and they can readily replace the gearbox of AEGs with the latest HPA engines in the market which are drop-in kits.
Red Army Airsoft writes about everything a Russian airsoft player needs to know about HPA airsoft.