Much depends on your locality. In rural jurisdictions you're more apt to find "barn guns" (H&Rs, Savages and the like), lever guns and .22LR long guns in economy format. Your urban areas tend to show a better mix with the very occassional 5 screw S&W, Python and sweet bolt gun.
The sad thing is that a lot of it comes down to the political nature of the chief LEO. An anti-gun Sheriff or Chief will most likely cut the guns. Unfortunately I've seen it happen to some gorgeous and historically pristine firearms.
Contrary to some opinions, police departments aren't interested in seizing, storing and cataloging guns. It wastes time, man power, money and in some cases, places a storage liability on the agency. Plus, the process of judicially disposing the firearms through the courts is a long and often arduous affair.