I have data with Reloader 7 (used with bolt action rifle!)
Reloader 7 is slightly slower than AA1680 and according to Speer Manual 13, 28 grains of AA1680 is max while 27 grains of RL 7 is max for the 125 grain bullet.
I have loaded 25 grains of RL 7 for a 150 grain Barnex TSX bullet. Therefore, 26 grains of AA1680 should be safe. Nevertheless, start with 24 grains of AA1680 and work up the load.
As a side note, I have also used 1.6cc (16.1 grains) of SR4759 with 150 grain Hornandy SP; accuracy is great .35" @ 100 yards for three shots