We are planning on making a Full Metal ACR(Masada PTS) using a CO2 system, cutting back on crappy electric missfires and other things. This system will allow you to adjust you FPS using a simple nozzle like a hose.
So far i only have a lot of tubing, it works as a gun, but has no body. So its still in development.
I will make about 20 this year, I will sell 1 for 300 dollars, but if you want upgrades (rails, scope, laser, etc.) it will go up. The price can be lowered just make an offer. They are not avaliable yet but order now! 20 avaliable.