That might have been a "tested" load, not commonly found in any reloading manual. If it is on the spread sheet from "J. B. Brooks", on the Parker site, he noted where each load was from, if he knew. His data has been very good. Some loads were published, some from powder websites and some had been tested for pressures and velocity. Checking volumes 1-5 of Lyman I see a similar load(s) using the Remington 2 7/8 hull with 57 primers, Volume 3 which is about the end of short ten loads. Do not have my BP Mighty 10 manual near me to check, but it might be listed in there. Now I need to figure out where my mighty ten manual is or who I loaned it to. You can purchase and download the BP Mighty ten manual. I need to think a bit and figure out which safe place I put it.
https://i.imgur.com/wDrma87.pngThis might make it easier for others to follow along and see where our information came from that you are trying to verify.