.375 Ultra Mag, 300 gr. bullet, 2760 fps, in a 10 lb. gun produces 36.15 ft. lbs recoil.
300 gr. handloads at 2,970 from a 7.5 pound rifle (including scope), no brake. I don't remember the exact powder charge off the top of my head, but about 98 or 99 grains, I think. I'll check when I get home. I used the Barnes calculator.
The calculator at handloads.com is incongruent with every other out there, but even with the load you mention, it calculates 45.63 FPE in a 10 pound gun, putting 93 grs. in for charge weight. I had to drop the charge to 60 grs. to get your figure. That's not enough powder to get reliable ignition in the necked down Jefferys case, let alone a respectable velocity. With my load and my rifle, that screwy calculator gives 69.99 FPE.
Plug in those numbers
here, it gives 83 ft/lbs at 27 FPS.
This one gives us 83 FPE and 26 FPS. The third
here is also on par. Need more?
You're new here (welcome aboard, BTW
), so I'll just tell you that if you pay attention to my posts, you'll find that I don't go off half-cocked, talking out of my @$$.