by Shooting Illustrated Staff posted on April 11, 2011 Guns Support NRA Shooting Illustrated DONATE Resurrecting the 6x45 mm cartridge, Spirit Gun Manufacturing's SGM-A41 is a high-performance, yet practical, take on the AR platform. In this article 6x45, AR, semi-auto rifles, Spirit Gun Manufacturing Related Stories Spirit Gun Manufacturing SGM-A41 Barrett REC7 in 5.56 NATO Gallery Colt Match Target M4 Case-Head Swipe Barrett REC7 in 5.56 NATO Most Popular Tech Wisdom: .300 Ka-Boom Marines Ditch 100-Year-Old Marksmanship Standards Affordable Firepower: Five Budget-Friendly AR-15s Review: Springfield Armory 1911 TRP 4.25-inch CC Getting Serious: Stepping Up Your Marksmanship Skills Make It Work For You