The bullet performs erratically once it hits its target--now, obviously, it does a GREAT job of hitting the target.
Some of the bullets drill right through without fragmenting or even yawing much...basically, a sub-30 caliber hole drilled through and through. Other bullets yaw quickly enough that they fragment, which causes a massive wound.
It shouldn't surprise you that many police snipers still use this round--they dream of the perfect 500 yard shot, however likely that is, and don't bother to research the terminal effectiveness of the bullet.
Many have gone to using Ballistic Tips, because they're reliable for expanding/fragmenting and designed to be plenty accurate at typical sniper distances. Even better are Hornady's A-MAX bullets. The 155 grain is favored due to its consistent perfromance in gel testing.