The Bureau of Alcohol, Tobacco, Firearms and Explosives on Thursday raised new concerns about surplus military ammo used in popular AR-15 rifles and pistols just days after pulling back on a proposal to ban the ammo because it could threaten police safety.

In a Senate Appropriations Committee hearing, ATF Director B. Todd Jones said all types of the 5.56 military-style ammo used by shooters pose a threat to police as more people buy the AR-15-style pistols.

"Any 5.56 round" is "a challenge for officer safety," he said. Jones asked lawmakers to help in a review of a 1986 bill written to protect police from so-called "cop killer" rounds that largely exempted rifle ammo like the 5.56 because it has been used by target shooters, not criminals.

His agency's move to ban the 5.56 M855 version was condemned by the National Rifle Association and majorities in the House and Senate and as a result was pulled back though not abandoned. At the hearing Jones said that nearly 90,000 comments on the proposal were received, many negative.

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