All the sites I've ever been to have had a limit of 350fps + 5% which basically means that the real limit is 370, though I don't know if that's the same of all sites.
I've got the G&G CM16 and although the quote on the box was 320fps it was actually shooting nearer 280fps. G&G seem to use the same gearbox in all the CM16 guns with different barrel lengths and the shorter the inner barrel the lower the FPS and vice versa (mine had a 247mm inner). I tried mine with a 509mm inner from one of my L85's and the fps was immediately nearer 350fps without changing anything in the gearbox, so check inner barrel length for probable FPS or ask the dealer to chrono it themselves for you before they send it out.
