Something with a MV over 3,000 fps.
BL-C(2) is the canister grade version of WC-846.
After the powder debate, Olin took powder on the fast side of WC-846, and christened it WC-844. This was to be used in the 5.56.
H-335 is the canister grade version of WC-844.
For ball powders, TAC, H-335, AA-2230, AA-2460, and even W-748 (if you do not push it), are better choices for a 55gr bullet.