draw a bead on someone/something

draw a bead on someone/something

or

take a bead on someone/something

mainly AMERICAN
If you draw a bead on a target, you aim your weapon at it. He had entered my office with a loaded gun and had drawn a bead on my heart. The small pale eyes squeezed shut as if he were taking a bead on her. Note: The bead is the small marker on top of the end of the barrel on some guns, which is used to aim at the target.
See also: bead, draw, on, something