The most accurate loads, .7 MOA, in my Model 600 have been with 250 gn bullets at something over 2400 fps.
250 Hornady, 59gn Reloader-15, 210 primer, 2.80" OL, 2445fps
250 Nosler, 53gn Benchmark, 210 primer, 2.80" OL, 2435fps
Substituting the 250 Speer for the Nosler gave 1.5" groups, 2415fps and shot to the same point of aim.
Reloader-15 was OK with the Hornady RN but under the 250 spitzers had to be squished too much for my taste, prompting the change to Benchmark.
225 bullets, Nosler and TSX, were very accurate at about 2470fps but groups opened up at higher velocities.
I would not increase the above loads at all and advise reducing them by at least 2 gn to start with.
Have not yet tried TAC but suspect that it might be ideal. The Ramshot manual suggests 53 to 59gn for 225gn bullets and 50.5 to 56gn for 250s.
One unerring mark of the love of the truth is not entertaining any proposition with greater assurance than the proofs it is built upon will warrant. John Locke, 1690