Iggy,
I found Varget to run best in my 223 (not imp) under 60 grainers, it was in the "crunch zone" under VM 55s at 26.8 grains. I had to charge and vibrate everything before seating at that load or I would get vertical stringing. Too much work...I just like to pump and dump on the Dillon.
Never mind that Varget tends to granule-jam every once in a while when poured into 22 cal necks. Messy.
You might be okay with a little more room in the Ack case, but I'm thinking because the TTSXs are on the long side, you might be crunchy in that 98-102 percent case-fill zone.
Because of that, I wound up going to H4895 under 55s but later found that 50s over 4895 was mo bettah.
I'll second what DD says. TAC is like 335 in meterability without the evil of temperature (which is why I left 335) -- I've done three other rifles with TAC loads at 50 and 55 depending on what the evil owners gave me to play with, and it was easy peasy to get good results. My feeling is TAC is much like 335, responding well to how hard a 55 pushes back against the gas column.
That is, IF you can find some TAC. I still have not seen any in over two years.
