Have you checked your velocity? A lower front chamber pressure (lower velocity) will help with reactivity. Are you using a level 10 bolt. If you are, then a shorter, lighter bolt spring will help make it more reactive. Also, try putting a shim or two in between the on-off halves. It will push the top oring up a bit higher which will reduce the distance the sear needs to travel to close off the air supply and release the bolt.
Except for the Automag in front, its usually the man behind the equipment that counts.