A&K SAW mags don't have a pressure switch. They have a sound sensor mounted in the "feed connector" (don't have a better name for it) part that connects into the gun. When it hears the mechbox firing, it automatically winds the mag. I fucking HATE the push-button mags. I have a G&P box mag with the pressure switch, and will try to mod it with a broken A&K mag so I can make it sound-activated too.