AKA's bolts are some of the best out there, in terms of airflow. I can't say I've used one myself, but having made bolts that roughly compare to an AKA Lightning and a Shocktech Superfly (internally, at least, they're midblock bolts), I picked up a good 25 FPS just from using a bolt with smaller internal passages and fewer drastic changes in flow direction or internal diameter.
Slik Edge III's are really nice, too, if you can find one in 2k+. Bought one back in the day, and even though the gun it's on has since been converted to a sniper, the bolt (and the CCM delrin back block) are staying
