by Shooting Illustrated Staff posted on February 7, 2012 Optics Support NRA Shooting Illustrated DONATE Designed expressly for AR-15's chambered in .223 Rem. or 5.56 NATO, the scope is reliable, functional and fast. In this article .223 Rem., 5.56 NATO, AR-15, ballistic reticle, Nikon, riflescopes Related Stories Nikon M-223 1-4x20 mm WATCH: SIG Sauer M400 Tread Core Rifle Systems Releases The All New Hardcore X Series Rifles For 2015 Nikon Unveils New P-223 Long-Range Riflescope With Dual Ballistic Compensation Nikon M-223 Riflescope Most Popular Shotgun Limitations Low Round Count Pistol Drills The Thinking Man’s Defensive Gun How To Get Ladies To Hate Guns Want To Improve Your Accuracy? Get a Grip. Review: Ruger Silent-SR ISB