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“The ban’s success in reducing criminal use of the banned guns and magazines has been mixed,” the report said, noting that because the ban had not yet reduced the use of large-capacity magazines in crime, researchers could not “clearly credit the ban with any of the nation’s recent drop in gun violence.”

The report said although the ban’s reauthorization or expiration could affect gunshot victimizations, predictions were “tenuous.” It said restricting the flow of large-capacity magazines into the United States from abroad might be necessary to achieve the ban’s desired effects.

But it said it was not known whether mandating further design changes in the outward features of semiautomatic weapons — such as removing all military-style features — would produce measurable benefits beyond restricting ammunition capacity.

Past experience also suggests that congressional discussion of broadening the assault-weapons ban to new models or features would raise prices and production of the weapons being considered, the report said, adding that if the ban were lifted, gun and magazine manufacturers could reintroduce weapons and magazines in substantial numbers. But, the report said, any resulting increase in crimes with assault weapons and large-capacity magazines might increase gunshot victimizations, “though this effect could be difficult to measure.”