that's a late model style. push/pull safety.
you may want to pull the bolt on that gun and see if it has a velocity adjuster in it. some Speed Demon bolts have a set screw in the end of it that can be adjusted to block the amount of air that flows through the bolt.
pull the bolt out of the gun and look in the end of it. if there is a set screw, turn it clockwise all the way. then put it back together and try that. then you can use your external adjuster shown in your pic.