User blog comment:Lord Vipertooth/sumerians/@comment-5157002-20160327213615

+15 HP is correct. I tested in the game, and the manual says the same thing, so I don't know where someone got the +30% figure from.

I don't know how the fire rate works, but from what I can judge, non-Sumerian Catapults fire every five seconds, while Sumerian Catapults use between 3 and 4 seconds (at game speed 1.0). This suggests that the manual info is correct - it fires 50% faster, rather than twice as fast.