<p>On Casters, probably. </p><p>On other classes, only if they use magic. Like Cu doing runes or Emiya doing trace on. </p>

<p>I don't know about that, since they don't actually have a physical body, just a form given shape by mana, I'm not even sure an origin bullet wouldn't just pass right through them, </p>

<p>no effects. Origin bullets stop the prana circulation inside a body, but a servant's body is made of pur prana from his core (brain and heart). In term of circuits there is no circulation. So it will workk like normal bullet and that's all. </p>

<p>Origin bullets mess up the magic circuits, and iirc servants do have magic circuits, like when they mention Artoria having a magic core instead because she has dragon blood. </p>

i see i m still looking for more opinions

<p>Well, the problem of servants is mainly they body, their essence of prana. They are made of magic, therfore they will affect them like magical weapons. But they will deal no great effect against them, which is why he doesn't even think about use them against servants (if we deal with the fact that servant's weapon are made of prana BUT can stop them, which is why he doesn't use them on servant, it's fair to assume that they are too much dense existence. </p><p>Also, just disappearing in uncorporeal form would render the bullet uneffective even if it's work at first time. </p><p>
</p><p>If humans have a body and that magic circuits are in their souls, Origins Bullets tend to force the magic they are circulating in their physics, which destroy them inside. But in a magical body, made to receive it, it woul at best force him to pass as ghost to get this bullet and it's effect out. </p><p>Also, the Origin Bullet affects Circuits because in case of magi it's the only magical natures in them. In a magical body, it's made up to damage it, so his function shall be basis. </p>

hmm i guess that answers the question

<p>it's change from whitch orgin bullet (if kiritsugu it's have some effect after al servants have prana and a kind nerve system (probly not soo deadly  at most slow them a litle bit)  also Emiya Alter's orgin bullets also work (after all its create millions blades in ther body :D ) </p>

<p>Emiya's Oriigin bullet is not truly an origin bullet, more kind of a door for his Reality Marble to go out inside a body. </p><p>For Emiya, well... Kiritsugu is in a servant system now, so if the bullets would have some effects, shall be indicated in his profile or in his Noble Phantasm :D </p>