Can anyone of you guys help me out? I'm looking into buying a GBBR m4/16 and converting it to a mk11 but most gbbr's highest fps that I've seen go only up to 410 fps. I want mine shooting 450-500 fps or maybe a little hotter if fields allow it but I'm wondering how is that possible? What parts do I need to upgrade to get it shooting around 500 fps.