You were told wrong. At least as far as 400 grain bullets are concerned. In one of the recent Lyman manuals (45 or 46, IIRC) there was data for a load that supposedly produced 2600 fps.
That data is no longer in the Lyman manual.
Why do you suppose that is?
A-Square's manual, "Any Shot You Want", has load data for R-22 as does the Hodgdon site. A-Square found that "pressures exceeded allowable limits" with R-22 when the velocity with the 400 grain Dead Tough bullet got to 2467fps.
I wonder what the pressures are at 2600 fps?
And....tweaking a cartridge that already gives you 5000 ft-lbs of energy seems like gilding the lily.
Pete