Mr. Bolt,
Keep in mind that the velocities listed from the old days were not absolutely accurate, they inflated numbers just the same as ammo companies in modern times. Also, you make no mention of your rifles barrel length, this can have a bearing on acceptable regulating velocities as well because the advertised velocities in the era were typically taken with 28” or 30” barrels. So trying for “factory” velocity combined with acceptable regulation with, say, a 26” barrel is a fools errand.
As Graeme Wright notes in his book (I paraphrase), if it regulates to satisfaction then your velocities are what they are.

NOTE:
The Graeme Wright book notes 56 grains of H4198 (with dacron filler) and the Woodleigh .500 cal 440 grain bullet at 1850’/sec as one of several loads that are “average regulating loads”.
- Mike