Legal move?

[DG]

The hands are never part of the bat, but throwing to an unoccupied base is sometimes a balk and sometimes not. This one is in the not category.

[mbyron]

C'mon, that's easy:

8.05 If there is a runner, or runners, it is a balk when:

(d) The pitcher, while touching his plate, throws, or feints a throw to an unoccupied base, except for the purpose of making a play.

If you judge that it was a bona fide attempt to make a play (NOT including "driving the runner back"), then no balk.