Gun Digest presents ... Cartridges of the AR-15 Noted gunwriter and AR-15 expert Patrick Sweeney lays out the ever-increasing field of AR-15 cartridges. Whether you're interested in AR-15s for home defense, long-range shooting, or hunting, there is surely a cartridge that meets your needs. Sweeney covers them all, from the 5.56 NATO/.223 Rem., to rimfires like .22LR, up to the .300 AAC Blackout, 7.62x40 Wilson, 6.5 Grendel,...