But Tellerve, the morningstars that I've seen have actual spikes on them. Perhaps you and I are thinking about two different things, but if that's what you're using for your case for making sais piercing damage, I think it's a stretch.
If you're thinking of a morningstar as just a different-shaped mace with knobby bits on it, then yeah, it ought to be just bludgeoning. But if you're thinking of a metal ball with spikes, then it NEEDS to be piercing, while the sai, which doesn't actually have a piercing point, does not.
Like I said: my stick techniques could make you think "piercing" when I do them, but they're bludgeoning. If someone can point me at a movie of someone doing sai techniques that they feel are piercing rather than bludgeoning, I'd be happy to take a look. My guess, though, is that they're pressure-point bludgeoning, aiming at the temple or the solar plexus to stun someone or knock the wind out of them, not to impale the dude on the weapon.
Iku Rex/Zhure, care to cite any source? All the martial artists I talked to said that the sai was originally a gardening implement. The "forger's tongs" thing is new to me, too, but it's also possible. Are you also arguing against the 'chucks as originally being rice flails, too, and the tonfa as originally being, shoot, I forget, the handle or something on a mill?
Personally, in my opinion and from my research as a martial artist, the "adapted from tools" theory holds more water for me than the "forged specifically as a weapon" theory.
At the time when these weapons were being used, anything that could be definitively classified as a weapon would have gotten the peasent carrying them killed. It was to their advantage to use things that had real purposes, so that they could say, "What, me, inciting unrest? No, I'm just carrying my gardening tools back home."
Beyond the legal stuff, they just didn't have the resources to go around designing weapons on the spot. Most martial arts weapons were adapted from common household items because that's all they had, and if the local samurai decided to play "test the sword on the peasant", the peasant's gardening tools were all he had to defend himself with.
Besides, the sai, while good against a sword, is nowhere near as good as, say, A SWORD (speaking as someone who's used both against both). If I had the resources to design a weapon from scratch, I'd make the epitome of weapondom -- a sword -- not a small club with hooks that could sort of defend against a sword okay if you had the right training.
