It doesn’t seem to relate to body size. I know small guys who can shoot horrendous rifles with no trouble, and immense humanoids who swoon at the sight of a .30/06. As a rule, the upper limit for most rifleman is a .41-caliber cartridge such as the .416 Remington or Rigby. Both fire 400-grain bullets at 2,300 fps or so. When you get up to the .458, with 500 grains at 2,000 fps (or a little less) and about 60 foot-pounds of recoil, most people would rather not, thanks. And with bigger cartridges like the .458 Lott and .450 Dakota 500 grains, 2,300 fps), even the toughest riflemen grow pale and begin to tremble.