The most important factor is the human one. Some people can shoot anything. I have a friend who shoots an 8-bore black powder double with a steel buttplate for fun, and I will not touch the thing. My own limit is a .458 Lott, which is about 70 foot-pounds of recoil. And that's assuming that the rifle is not too light, has a straight stock, and a good recoil pad. Beyond this I do not go because there's no sense to it. If there's something you can't drop with a Lott, maybe you need an RPG. If you go beyond your limit, you will develop a flinch, guaranteed, wreck your back, and detach your retinas.