get a bead

-Get something/someone on the scope before shooting.
-In American English when you focus narrowly on something or define it carefully you “get a bead” or “draw a bead” on it. In this expression the term “bead” comes from the former name for the little metal bump on the end of a gun barrel which helped the shooter aim precisely at a target.

I get a bead on that animal and I am gonna shoot it!