I can confirm it's rated for 0.20s, I chronoed my stock Kraken AK-47 last week and it was shooting ~340 FPS with 0.25s. Which would be ~380 FPS with 0.20g BBs.
Lovin' this gun, had it 3/4 of a year, gone through 4000 BBBastards without a single issue.
Doing some preventative maintenance soon thought. Ordering some Steel Bushings, Shims, M90 Spring, Tightbore Barrel, Bearing Spring Guide, Cylinder and Gear Grease. Gonna be sweet.