I have 3 ar rifles. One in 5.56 mm, one in 6.8x43 mm, and one in 7.62x39 mm. After some target shooting, and some varmit shooting and deer hunting, I really like the 6.8 spc. It is almost as accurate as the 5.56, it seems to be more accurate than the 7.62x39 and hit almost as hard as the 7.62x39 154 gr load. the 6.8 slams Groundhogs hard and does real good on deer. For the 2008 and 2009 deer seasons I used the 7.62x39 with the Cor-Bon 154 gr loads one dropped in its tracks (87 yds) and the other I shot at about 125 yds, and I had to track but it only went about 400 yards so that not bad, I have seen deer shot with 308 Win go farther, really not bad at all for the 7.62x39. This past season I used the 6.8 and at 160 yards went down after running 40 to 50 yards or so. Not too bad. What has been your opinion on the 6.8x43 mm SPC V/S the 7.62x39 mm?