[quote=Neobullseye]
How does he even lift that thing, let alone with one hand?! That's more ridiculous than the Buster Sword >_<
[/quote]

Because Shirou is an idiot that will inflict tremendous harm to himself to do things that he shouldn't be able to do. :p

Also, magic. Magic is very involved. Well, magecraft, but magic sums it up well enough.