The DoJ, NIJ, CDC and NRC have all conducted studies, at tax payers expense, which have studied the impacts that banning specific firearms features (e.g. "assault weapons") have on crime. The conclusions of each of those studies is that bans on specific firearms features have had no measurable impact on crime. Total violent crime rates have continued to decrease steadily since 1973 (DoJ statistics) even as gun ownership has remained at a relatively constant percentage of the growing U.S. population.
These studies and statistics, sponsored by the Executive Branch, need to acknowledged by the Executive Branch.