While a .460 WTBY case necked up for .510" 600gr. bullets isn't the same as a .500 Jeffery, the recoil and performance is in the same general ball-park. With 125gr. 3031 (NOT LOADING DATA TO USE) with a 600 gr. Barnes, the velocity was supposed to be 2,700fps. From the 8 1/2 pound rifle, recoil was excessive & one shot was to much. 10.5 pounds would certainly not be excessive for your Jeffery and 11 pounds might be better.
: In those days, I had a reputation for liking recoil, but that one was too much.