Defense Distributed tests 3D-printed 5.7mm X 28FN AR Lower receiverhttp://www.engineering.com/3DPrinting/3DPrintingArticles/ArticleID/5038/Defense-Distributed-Tests-Their-Mettle.aspx?goback=%2Egde_88762_member_192938862 by bradleysmith • 14 years ago 1 0 14 years agoENengineering.com