Hey guys! I was rattling your collective cages.
As was pointed out, many departments don't have the funds and/or the smarts to see the value in a properly set up shotgun and training. A number of Alaska agencies have gone to Vang Comp shotguns with MMC sights because they found that they work. The problem is that a 14" 870 with MMC sights, Vang Comp mods and a Surefire light costs as much as 3 Police Magnums.
It may surprise you to hear that a lot of individual officers buy 870s with all the goodies after taking shotgun classes at places like Gunsite, Blackwater and Frontsite.
A note to Dave McC. All the Alaska Dept. of Corrections 870 barrels have been Vang Comped. I guess they saw some value in having tight buckshot patterns out to 25 yards.
As far as speed goes, I wish you could see the video of a trained officer shooting 6" plates at 12 yards with a 14" Vang Comp 870 and MMC sights. He knocked over all 6 plates and all 6 shells were still in the air.