I've found that Ramshot's Nato Data for TAC needs to be backed off by about .2 to .3 grains in winchester and LC brass. I load the 70 grain tsx with 25.7 grains and get 2862 FPS out of a 16 inch barrel with an SD of 5.7. I'd start at 23.5 and work up towards 24.5 with the 77.