Depends on how scrambled. If you take a porcelain vase and drop in on a hard floor, it will shatter. But you can put the pieces together. The bits of brain may be indistinguishable to the human eye, but unless they are literally creamed, the individual cells separated from each other on an individual level (a possibility - I don't know the specifics), it might be possible to re-assemble the bits.
Cells are not so resilient that a bullet will simply separate them and leave them otherwise intact. It may or may not be possible in principle to tell "which cell goes where" if you were to separate them, but a bullet to the head doesn't even give you something that convenient to work with.
From "Academics Doubt Impact of Osama bin Laden’s Death":
See also Lost Purposes, The Importance of Goodhart's Law, & Faster than Science.