the AR 10 type rifles I have had, maybe 3 of them were in 308,IIRC they were 2-3 MOA type guns in my hands anyway, (even had an FAL once) so not in my hands would they be 500+ yard guns. The bolts I have had and still own are much more accurate and I have a couple in 6.5CM. So why would I want a long range and weaker cartridge in a gun that is not long range capable? Of course this is just my opinion, maybe there are flaws in my thinking, but if I have a 2-3 MOA gun, why not have the most powerful 2-3 MOA gun possible? Again, maybe the 6.5 CM SFAR is a 1/2 MOA gun and I am mistaken, if it were a true 1 moa gun I sure would be interested. If it were a 1-2 MOA gun in 308 I would be interested, seems like there still is some controversy over its performance or quality control.
