Miles,
I don't know how you managed to get only 3000 fps with the 53 TSX and TAC. I've loaded TAC with 50-55 grain bullets in a BUNCH of .223's and the lowest velocity I've seen with Ramshot data is about 3150 with the 50-grain Ballistic Tip--in my 16" barreled Bushmaster AR-15.
In normal-length barrels TAC normally gets 3300+ with 50-53 grain bullets. In a 26" 700 it gets over 3400. Maybe you just have a special lot of powder?
20 inch LTR barrel that liked them jammed into the lands. 3000 FPS wasn't a max load even then, but it just went together and shot good so I used it.
I probably could have gotten more out of it and kept accuracy too had I backed off and matched dimensions to the BLC-2 loads, but it just fell together and shot so nice I left it because it would do everything I needed it to.
From prior work with BLC-2 I already knew TAC wasn't going to get close to that powder's capability. I was more interested in looking at deer killed with 53 grain TSXs. I already was 95% certain of what I would see and simply hedged the bet that 300 FPS wasn't going produce a noticeable difference near 3000 FPS. Some day I'll revisit that and slide the range down to where 300 FPS does produce a difference just to see where that occurs.
Edited to add:
Out of curiosity I went back and reviewed the load notes. The TAC load is is not far above a minimum load with plenty of overhead available. The BL-C2 loads are pushed harder for specific rifles. With a 53 grain TSX I don't think safe max loads would come out much different.
