PS, I've played with the 70 AB in my hogslayer ARs, which I believe are 1:8s (both are LaRue barrels). I chose AR-Comp because I have a lot of it on hand and it was not slated for any other use...I had no trouble getting near-MOA performance using 23.0 grains of the stuff. I'm still not very confident of my shooting off a bipod, or even the AR platform itself, so it may well shoot much better than I do.
I'm getting about 2800 fps out of the 18-inch barrels with this load (chronographed). According to QuickLOAD, AR-Comp is an excellent choice to go with this bullet.
BTW, I had been waiting for months to get my hands on more 70 ABs from SPS...when I finally saw them the other night I tried to buy 500 more, but could only get 450. I guess I got the last of them! I bet it'll be another year before we see them again.