The SWORD Billet machined Mk16 upper receiver is designed to be compatible with military specification lowers. That is where the similarities between “mil-spec” AR uppers and the Mk16 end. SWORD has designed the Mk16 to be the most rigid, durable and precise upper receiver on the market. We have achieved this by milling the complete unit from aircraft grade 7075 billet aluminum material using the most accurate CNC machines available to perfect tolerances every time. Changing the lines and increasing material in crucial areas allow for a more rigid receiver. The Mk16 gives you a more durable upper with increased sustainability and accuracy.