I've loaded the Speer 70gr Semi-Spitzer up with BLC2 and Varget per Speer & Hodgdon's published data. Varget achieved 125fps faster velocity, both with good groups (< 1.5" at 100 yards). I didn't like the recommended 2.140", so I loaded up at 2.255" without any problems.
Varget gave very impressive velocities out of a 16" AR-15 with slightly flatten primers at Max charge. I backed off of max by 1gr and got a nice shooting round @ 2775fps for 1198 ft-lbs.
Thought about trying TAC, but I was pretty happy with the Varget load, although TAC would meter better.
Good luck, work your loads up carefully.
