Bill Flemming's book lists numerous loads for 577 3 1/4 BPE, nitro for black and Nitro. The BPE loads range from 160 gr BP/560 gr bullet to 167 gr bp/650 gr bullet. Nitro for black loads were 65 gr cordite/560 gr bullet to 75 gr cordite/650 gr bullet. Nitro loads were 90 gr cordite/650 gr bullet to 100 gr cordite/750 gr bullet. He speculates the long case fell out of favor because the shorter 3" rounds could do the same without the extra length. No velocity or energy figures were given. Hope this helps.