Mesatchornug
NES Member
Arguably, the AR's DI system is a weirdo indirect piston. "Real" DI systems (IIRC) look more like what you've just postulated for gas blowback, which I'll admit I'm insufficiently experienced to comment on.Maybe they should call piston systems indirect impingement. What is gas blowback - is that just gases from the chamber blow a bolt back as opposed to a gas tube directing gas to the bolt?