Treblaine said:
Also as demonstrated in the movies he can only control small amounts of metal over a distance of about 100 feet. Look at his "plastic prison":.
First, what about when he moves the Golden Gate Bridge in the 3rd movie. I do believe that that bridge is longer than 100ft.
OT: Lets set up the scenario with a few more details.
First: The only effective material for a bullet is one made out of some kind of metal. As somebody said earlier, other materials would either disintegrate or shatter. So we can assume that the bullet is made out of some kind of metal.
Second: Magnetic fields are not limited to manipulating only iron, nickle, and cobalt. All Materials fall into three categories when dealing with magnetism- Ferromagnetic (strongly attracted to magnetic fields, eg: iron), Paramagnetic (weakly attracted to magnetic fields, eg: platinum and oxygen), and Diamagnetic (weakly repelled from magnetic fields, eg: copper and water)
More proof that magnetic fields affect more than metals can be found at your local hospital in the form of an MRI machine, which uses magnetic fields to observe the brain, which is obviously not metal.
So we can also assume that, given a strong enough magnetic field, any object could be attracted or repelled.
Third: Magneto can "sense" metals, as seen in the second movie when he "senses" that the guard has too much iron in his blood, and in all the movies when he "senses" Wolverine's adamantium skeleton.
So, given the scenario. A sniper shoots a bullet, which is limited to metals, from far enough away that Magneto doesn't know he is there. This means that there is a period of time between the bullet leaving the barrel and hitting it's intended target. Now Magneto can sense metals, so we could probably assume he would notice if one was traveling above two times the speed of sound.
Now the question is, can he create magnetic fields centered only around him, or elsewhere? It turns out that it doesn't matter, because if he could create a field elsewhere he could simply create it wherever he had to to stop the bullet. If he can only center them on himself then we can use the fact that magnetic fields become exponentially stronger the closer you are and say that the closer the bullet was to him when he repels it, the easier it would be to repel.
And lastly, could he stop one that wasn't made of a strongly magnetic material. Obviously if it was a Ferromagnetic material then it would be easy. If it was a Paramagnetic material it would depend on how strong the field was. I'm inclined to believe he could make one strong enough seeing as he can rip the Golden Gate Bridge from it's foundation. And if it was a Diamagnetic material, such as copper, then all he would have to do is create a strong field and it would be deflected.
That's my two-cents anyway.