Gun Control: 3D-Printed AR-15 Lower Receivers August 22, 2018. IN10957 “The possibility that criminals could use three dimensional-printing (3D-printing) technology to produce “untraceable” firearms, including AR-15s, is an issue of growing concern for some lawmakers. It overlaps in part with the issue of 3D-printed “undetectable” firearms discussed in a previous Insight (CRS Insight IN10953, Gun… Continue Reading