I've used it some with 125-150 gr. bullets in the .308. As said it works quite well and has an anti fouling agent added to it.
Ramshot's Big Game apprently offer more speed with 180 gr. bullets. See their website.
TAC tops out at about 44.5 grs. and 2734 fps. in a 24 inch tube with the SRA 175 gr. MatchKing bullet and about 2621 with 42.4 grs. with the SRA 180 gr. GameKing.
What I noticed is that the sweet spot is pretty specific with TAC. Usually near or at the top end. At least in the .308 and with lighter bullets in the .280. E
