I don't know how to figure the recoil but I used to shoot a Ruger #3 in .45-70 for fun with 500 gr. jacketed bullets at 350 fps less than a .458 Win. Mag. I am going off memory but I think that was around 1800 fps. I only shot it offhand, eschewing the bench with that little lightweight gun, but I found the recoil to be fun, actually. Muzzle flip was "showy", too. I can't recall what it weighed, but it was definitely light. It was replaced by a No. 1 in the same caliber, which I still have.

May God bless America and those who defend her.