Criminals increasingly are choosing high-powered firearms such as assault weapons, a new survey of 166 U.S. police agencies shows.

Nearly 40% of the departments reported an uptick in the use of assault weapons, according to the Police Executive Research Forum, a law enforcement think tank. In addition, half reported increases in the use of 9mm, .40-caliber and 10mm handguns in crimes - among the same types of weapons that police use. The survey offers one of the broadest indications of officers' concerns about the armed threat from criminals involved in murder, assault and other weapons-related offenses.

Among problems cited by police officials in interviews about the survey:

•Chicago: Seizures of assault weapons are up, from 264 in 2008 to 313 in 2009. Overall, 7,785 weapons were recovered this year, up from 6,963 in 2008. Chicago Police Superintendent Jody Weis says there is evidence that more weapons are being used per shooting and more shots are being fired.

•Milwaukee: Semiautomatic 9mm and .40-caliber handguns were used in the non-fatal shootings of six city police officers over a 21-month period, ending Sept. 30. "The quality of weapons (used by criminals) has changed dramatically in the past decade," Police Chief Edward Flynn says.

•Louisville: Weapons-related arrests are on pace to rise for the second straight year in 2009. "We're seeing higher-caliber weapons, a lot more automatic weapons," Police Chief Robert White says. "The criminals know you don't take a bow-and-arrow to a gunfight."

National Rifle Association spokesman Andrew Arulanandam says officers' concerns are largely misplaced: "The real issue is the high-caliber criminal, not the high-caliber firearms." He says repeat offenders are overwhelming the system and could increase as states send fewer to prison to cut costs.

Paul Helmke, president of the Brady Campaign to Prevent Gun Violence, says the high-powered weapons endanger officers. If police say there's a problem, "public officials should be listening."