@nytrogyn:
I think kabuto's secret is a wind dial or something that allows the ammo to fly further, faster, and with more accuracy.
I'm thinking it has a Reject Dial in it because that would greatly enhance the power. Plus, it's a slingshot type thing, so maybe it can absorb the Reject when it kicks back. It also long, which means it provides pretty good range too if he needs to smack someone with it in close combat. Also, the reject could be used to fire larger projectiles with more power and greater distances.
I thought I'd drop my prediction here on Lucci … he's either toast, or definitely toast by next chapter. He looks done though. I think I'm going with the guys who said that if Luffy can't take him out then it would basically going against Luffy's dream of becoming the strongest. This whole douriki thing etc. would also be pointless. Oda has very nicely organized a tier for us to see where everyone is at respectively with the douriki points system. Luffy has obviously separated himself from Zoro and Sanji, while those two have also separated themselves from the rest of the crew. Ah well, I better get back to work I'm slacking. I can't wait for the spoilers for Ch. 422.